Report of Contributions - CERN Indico

28th Texas Symposium onRelativistic Astrophysics

Report of Contributions

https://indico.cern.ch/e/texas2015

28th Texas Symp … / Report of Contributions Linearly shielded modifications of …

Contribution ID: 1 Type: Talk

Linearly shielded modifications of gravityWednesday, December 16, 2015 2:43 PM (21 minutes)

Modifications of gravity arising in the presence of a nonminimally coupled scalar field and capableof accelerating the expansion of our Universe can be suppressed at the linear level of cosmologicalperturbations, only introducing deviations from concordance cosmology at the largest observablescales. I will classify the theory space capable of this mechanism in the effective field theory ofunified dark energy and discuss potentially observable signatures in relativistic effects of galaxyclustering near the Hubble scale.

Primary author: Dr LOMBRISER, Lucas (University of Edinburgh)

Presenter: Dr LOMBRISER, Lucas (University of Edinburgh)

Session Classification: 03 - Modifications of gravity

January 12, 2022 Page 1

28th Texas Symp … / Report of Contributions The m-z relation for type Ia super …


The m-z relation for type Ia supernovae, locallyinhomogeneous cosmological models, and the nature

of dark matterMonday, December 14, 2015 3:19 PM (26 minutes)

The magnitude-distance relation for type Ia supernovae is one of the key pieces of evidence sup-porting the cosmological “concordance model”. The resulting constraints on the cosmological pa-rameters are often derived under the idealized assumption that the universe is perfectly homoge-neous (at least as far as light propagation is concerned). However, we know that the universeis not homogeneous on small scales, and we know that such local inhomogeneities affect lightpropagation and hence distances which depend on angles, such as the luminosity distance. Whatdoes this mean for constraints on cosmological parameters derived from the magnitude-distancerelation for type Ia supernovae? And, conversely, what does the fact that these constraints, whenlocally homogeneity is assumed, agree with other constraints mean for the nature of dark matter?

Primary author: Mr HELBIG, Phillip (*)

Presenter: Mr HELBIG, Phillip (*)

Session Classification: 04 - Dark energy


28th Texas Symp … / Report of Contributions IceCube and the discovery of high- …


IceCube and the discovery of high-energy cosmicneutrinos

Thursday, December 17, 2015 9:00 AM (35 minutes)

The IceCube project has transformed one cubic kilometer of natural Antarctic ice into a neutrinodetector. The instrument detects more than 100,000 neutrinos per year in the GeV to PeV energyrange. Among those, we have recently isolated a flux of high-energy cosmic neutrinos. I willdiscuss the instrument, the analysis of the data, and the significance of the discovery of cosmicneutrinos. The high cosmic neutrino flux observed implies that a significant fraction of the radia-tion in the non-thermal universe, powered by compact objects from neutron stars to supermassiveblack holes, is generated by accelerating protons and not just electrons.

Primary author: Prof. HALZEN, Francis (IceCube/WIPAC)

Presenter: Prof. HALZEN, Francis (IceCube/WIPAC)

Session Classification: Plenary talks


28th Texas Symp … / Report of Contributions Experimental tests of general relat …


Experimental tests of general relativity in binarysystems

Wednesday, December 16, 2015 10:10 AM (35 minutes)

The radio sky is a fascinating laboratory for a very wide rangeof physics. The laws of nature can be probed at a fundamentallevel, in particular when observing the most extreme matter inthe observable universe - neutron stars. When they are visibleas radio pulsars they can act as cosmic clocks that becomeespecially interesting if they have a binary companion. Indeed,binary pulsars provide indispensable laboratories for precision tests of gravity. Effects that can bestudied in great detail include the emission ofgravitational waves, Shapiro delay, orbital precession and more. Butalso fundamental differences between general relativity andalternative theories of gravity can be probed, such as possibleviolations of the strong equivalence principle, preferred frameeffects or the existence of gravitational dipole radiation or scalarfields. Also the effects of spin precession in stronglyself-gravitating bodies can be studied by observing effects ofgeodetic precession. These and an other tests, and the comparisonwith other methods, will be discussed.

Primary author: Prof. KRAMER, Michael (Max-Planck-Institut fuer Radioastronomie)

Presenter: Prof. KRAMER, Michael (Max-Planck-Institut fuer Radioastronomie)



28th Texas Symp … / Report of Contributions XMM-Newton’s impact on Relativ …


XMM-Newton’s impact on Relativistic Astrophysics:Black Holes

Tuesday, December 15, 2015 2:00 PM (21 minutes)

With about 300 refereed papers published each year, XMM-Newton is one of the most success-ful scientific missions of ESA ever. Observations of Galactic as well as supermassive black holes,where relativistic effects have to be accounted for, play a major role in XMM-Newton’s observingprogram. The main focus of the talk will be the discussion of scientific highlight results based onXMM-Newton observations of compact, relativistic objects during the last years. X-ray observa-tions provide a unique opportunity to study the vicinity of compact objects, i.e. the region wherethe strong gravitational field acts and allow the determination of black holes spin.

Primary author: SCHARTEL, Norbert (ESA)

Presenter: SCHARTEL, Norbert (ESA)

Session Classification: 16 - Black holes


28th Texas Symp … / Report of Contributions Progress on the knowledge of mag …


Progress on the knowledge of magnetic fields inneutron stars


With about 300 refereed papers published each year, XMM-Newton is one of the mostsuccessful scientific missions of ESA ever. Neutron stars are classical targets of X-rayobservatories and consequently huge expectations were accompanying the lunch ofthe spacecraft. Contrary to expectations, the spectra of neutron stars were generallyfound continuum dominated exclusive any spectral features.The situation has dramatically changed during the last years as variable spectralfeatures were detected for several neutron stars and magnetars. These findings allowunique view of the different magnetic field components of neutron stars. In the talk Iwill illustrate the achieved progress with selected highlights of XMM-Newtonobservation of neutron stars.

Primary author: SCHARTEL, Norbert (ESA)

Presenter: SCHARTEL, Norbert (ESA)

Session Classification: 18 - Gal. accel. & pulsars


28th Texas Symp … / Report of Contributions The equation of state of dense matter


The equation of state of dense matterTuesday, December 15, 2015 11:20 AM (35 minutes)

With an average density higher than the nuclear density, neutron stars provide a unique test bedfor nuclear physics, quantum chromodynamics, and nuclear superfluidity. Determination of thefundamental interactions that govern matter under such extreme conditions is one of the majorunsolved problems of modern physics and - since it is impossible to replicate these conditions onEarth - a major motivation for future telescopes. Relativity, however, plays a key role in effortsto measure the equation of state. It is using relativistic effects that we measure neutron star massand radius, and it is the relativistic equations of stellar structure that relate mass and radius to theequation of state. I will review our current state of understanding of the dense matter equation ofstate, and the prospects for better constraints to come from future telescopes.

Primary author: Prof. WATTS, Anna (University of Amsterdam)

Presenter: Prof. WATTS, Anna (University of Amsterdam)



28th Texas Symp … / Report of Contributions Towards fundamental physics fro …


Towards fundamental physics from cosmologicalsurveysTuesday, December 15, 2015 10:10 AM (35 minutes)

Surveys of the cosmic microwave background and large galaxy surveys of the next decade carryimmense promise for measurements of new physics beyond the Standard Models of cosmology andparticle physics. However, these observations are complicated by multiple sources of systematics,either intrinsic, observational, or instrumental, which must be carefully controlled in order to makereliable inferences from the data about fundamental physics. In this talk I will show how some ofthese real-world effects impact the data. I will present an example of how spatially-varying observ-ing conditions impact measurements of fundamental physics (such as primordial non-Gaussianity)from galaxy surveys, and discuss techniques that can be used to control these systematics. I willpresent a comprehensive survey of the capabilities of future CMB experiments, taking account ofGalactic foregrounds and the effect of lensing by intervening large-scale structure. Incorporatingthese effects, I will present forecasts for the constraining power of these experiments in terms ofinflationary physics, the neutrino sector, and dark energy parameters.

Primary author: Prof. PEIRIS, Hiranya (University College London)

Presenter: Prof. PEIRIS, Hiranya (University College London)



28th Texas Symp … / Report of Contributions The Blandford-Znajek theory revis …

Contribution ID: 18 Type: Poster

The Blandford-Znajek theory revisitedWednesday, December 16, 2015 6:19 PM (3 minutes)

How powerful relativistic jets are generated is still one of the most important topics of the modernastrophysics. One of the most interesting and adopted theories was developed by Blandford andZnajek in 1977 with reference to jets from black holes. In the present work, I would like to drawthe attention on some relatively unexplored features of the theory, with particular reference to theanalogies with electromagnetic generators.

Primary author: Dr FOSCHINI, Luigi (National Institute for Astrophysics - INAF)

Presenter: Dr FOSCHINI, Luigi (National Institute for Astrophysics - INAF)

Session Classification: 14 - Disks and jets


28th Texas Symp … / Report of Contributions High-resolution SZ cartography of …


High-resolution SZ cartography of clusters ofgalaxies with NIKA ath the IRAM 30-m telescope

Monday, December 14, 2015 3:25 PM (20 minutes)

Thermal Sunyaev-Zeldovich effect (tSZ) is a powerful probe that has been proved to be comple-mentary with respect to traditional methods of cluster detection (e.g. X-ray, optical). Previousarcmin resolution tSZ observations (e.g. SPT, ACT and Planck) only allowed detailed studies ofthe intra cluster medium morphology for low redshift clusters (z < 0.2). Thus, the developmentof precision cosmology with clusters requires high angular resolution observations to extend theunderstanding of galaxy cluster towards high redshift.NIKA2 is a wide-field (6.5 arcmin field of view) dual-band camera, operated at 100 mK and contain-ing ~ 5000 KID (Kinetic Inductance Detectors), designed to observe the millimeter sky at 150 and260 GHz, with an angular resolution of 18 and 12 arcsec respectively. The NIKA2 camera will beinstalled on the IRAM 30-m telescope (Pico Veleta, Spain) in September 2015. The NIKA2 tSZ obser-vation program will allow us to observe a large sample of clusters (50) at redshifts between 0.5 and1. As a pathfinder for NIKA2, several clusters of galaxies have been observed at the IRAM 30-mtelescope with the NIKA prototype to cover the various configurations and observation conditionsexpected for NIKA2.

I will present recent tSZ observations of clusters of galaxies with the NIKA prototype at the IRAM30-m telescope together with the forthcoming tSZ observation program with the NIKA2 camera.

Collaboration

NIKA2 Collaboration

Primary author: MAYET, Frédéric (CNRS)

Presenter: MAYET, Frédéric (CNRS)

Session Classification: 08 - Cosmic microwave background

28th Texas Symp … / Report of Contributions Understanding supernova kicks an …


Understanding supernova kicks and black-hole spinsin Galactic X-ray binaries


In recent years, an increasing number of proper motions have been measured for Galactic blackhole (BH) X-ray binaries (XRBs). When supplemented with accurate determinations of the compo-nent masses and spin rates, orbital period, and donor luminosity and effective temperature, thesekinematical constraints harbor a wealth of information on the systems’ past evolution. We devel-oped an analysis that allows us to consider all this available information and reconstruct the fullevolutionary history of XRBs back to the time of core collapse and compact object formation. Theconstraints on compact object progenitors and kicks derived from this are of immense value for un-derstanding compact object formation and exposing common threads and fundamental differencesbetween BH and neutron star formation.

Galactic field low-mass XRBs (LMXBs), like the ones for which BH spin measurements are avail-able, are believed to form in situ via the evolution of isolated binaries. In the standard formationchannel, these systems survived a common envelope phase, after which the remaining helium coreof the primary star and the subsequently formed BH are not expected to be highly spinning. How-ever, the measured spins of BHs in LMXBs cover the whole range of spin parameters from a~0 toa1. In this talk I propose that the BH spin in LMXBs is acquired through accretion onto the BHduring its long stable accretion phase. I find that in all Galactic LMXBs with measured BH spin, theorigin of the spin can be accounted by the accreted matter. Furthermore, based on this hypothesis,I derive limits on the maximum spin that a BH can have depending on the orbital period of thebinary it resides in, and give predictions on the maximum possible BH spin of Galactic LMXBswhere a BH spin measurement is not yet available. Finally, I will discuss the implication that ourfindings have on the birth black hole mass distribution.

Primary author: FRAGKOS, Anastasios (University of Geneva)

Presenter: FRAGKOS, Anastasios (University of Geneva)

Session Classification: 15 - Binaries


28th Texas Symp … / Report of Contributions Consequences of extended hologra …


Consequences of extended holographic Ricci darkenergy in chameleon Brans-Dicke cosmology

Accumulating the observational data of Supernovae Type Ia(SN Ia) by the year 1998, Riess et al.(1998) in the High-redshift Supernova Search Teamand Perlmutter et al. (1999) in the SupernovaCosmology Project Team have independently reportedthat the present universe is accelerating. The source for this late-time acceleration was dubbed“dark energy” (DE), which is distinguished fromordinarymatter species such as baryons and ra-diation, in the sense that it has a negative pressure.In the present work, we have studied somefeatures of the generalized Brans-Dicke (BD) model in which the scalar field is allowed to couplenonminimally with the matter sector. Extended holographic Ricci dark energy (EHRDE) has beenconsidered in the above framework of BD cosmology. Some restrictions have been derived for theBD parameter , and a strongermatter-chameleon coupling has been observed with the expansionof the universe. In this framework, the equation of the state parameter of EHRDE has behavedlike quintom. Also, we have reconstructed the potential and coupling function for BD model forthe EHRDE. It has been observed that the potential function is increasing as the matter-chameleoncoupling is getting stronger.

Primary author: CHATTOPADHYAY, Surajit

Presenter: CHATTOPADHYAY, Surajit


28th Texas Symp … / Report of Contributions The X-ray Integral Field Unit for t …


The X-ray Integral Field Unit for the second largeclass ESA mission Athena

Thursday, December 17, 2015 3:25 PM (20 minutes)

The Athena mission is the second large mission of ESA with an expected launch date of 2028. Thedata will be gathered by a very large mirror (2 m2) with a 5 arcsec resolution. Athena will have twoinstruments: the Wide Field Imager combines a large field of view (40 x 40 arcmin2) with Si-classenergy resolution and the X-ray Integral Field Unit (X-IFU) which enables high spectral resolutionover a 5’ equivalent diameter field of view. This instrument employs calorimeters which are read-out by Transition Edge Sensors (TES) which operate around ~100 mK. In its baseline configuration,it is made of a monolithic array of 3840 single pixels with a spectral resolution of 2.5 eV. The datawill be read-out using Frequency Domain Multiplexing and the cooling system will enable anoperational lifetime of more than 5 years. In this paper, we will present the top-level instrumentperformance and associated science drivers. In addition we will demonstrate the unique capabilityof this instrument for some relevant science cases.

The X-IFU will be provided by an international consortium led by France, The Netherlands andItaly, with ESA member state contributions from Belgium, Finland, Germany, United Kingdom,Poland, Spain, Switzerland together with the United States and Japan.

Collaboration

J.W. den Herder (NL), D. Barret (FR), L. Piro (IT) on behalf of the X-IFU Consortium

Primary author: Dr DEN HERDER, Jan-Willem (SRON)

Co-authors: Dr PIRO, Luigi (INAF/IAPS); Dr BARRET, didier (IRAP)

Presenter: Dr DEN HERDER, Jan-Willem (SRON)

Session Classification: 20 - Future challenges and experiments


28th Texas Symp … / Report of Contributions Force sensor for chameleon a cand …


Force sensor for chameleon a candidate for darkenergy


The search for non-Newtonian forces has been pursued following many different paths. Recently itwas suggested that hypothetical chameleon interactions, which might explain the mechanisms be-hind dark energy, could be detected in a high-precision force measurement. In such an experiment,interactions between parallel plates kept at constant separation could be measured as a function ofthe pressure of an ambient gas, thereby identifying chameleon interactions by their unique inversedependence on the local mass density. During the past years we have been developing a new kindof setup complying with the stringent requirements of the proposed experiment. In this poster wepresent the first and most important part of this setup—the force sensor. We discuss its design,fabrication, and characterization. From the results of the latter, we derive limits on chameleoninteraction parameters that could be set by the forthcoming experiment. Finally, we describe theopportunity to use the same setup to measure Casimir forces at large surface separations withunprecedented accuracy, thereby potentially giving unambiguous answers to long-standing openquestions

Primary author: ALMASI, attaallah (vu university of amsterdam)

Co-authors: Prof. IANNUZZI, Davide (Vu university of amsterdam); Dr SEDMIK, René (VU uni-versity of Amsterdam); BRAX, philippe (CEA)

Presenter: ALMASI, attaallah (vu university of amsterdam)



28th Texas Symp … / Report of Contributions Kaluza-Klein cosmological model i …


Kaluza-Klein cosmological model in f (R, T ) gravitywith $\Lambda(T)


A class of Kaluza-Klein cosmological models in f(R, T ) theory ofgravity have been investigated. In the work, we have considered thefunctional f(R, T ) to be in the form f(R, T ) = f(R) + f(T ) withf(R) = λR and f(T ) = λT . Such a choice of thefunctional f(R, T ) leads to an evolving effective cosmologicalconstant Λ which depends on the stress energy tensor. Thesource of the matter field is taken to be a perfect cosmic fluid.The exact solutions of the field equations are obtained byconsidering a constant deceleration parameter which leads to twodifferent aspects of the volumetric expansion namely a power law andan exponential volumetric expansion. Keeping an eye on theaccelerating nature of the universe in the present epoch, thedynamics and physical behaviour of the models have been discussed.From statefinder diagnostic pair we have found that the model withexponential volumetric expansion behaves more like a Lambda cold dark matter (ΛCDM)model.

Primary author: Prof. SAHOO, Pradyumn Kumar (Birla Institute of Technology and Science-Pilani,Hyderabad Campus)

Presenter: Prof. SAHOO, Pradyumn Kumar (Birla Institute of Technology and Science-Pilani, Hy-derabad Campus)



28th Texas Symp … / Report of Contributions Cosmology with the Planck all-sky …


Cosmology with the Planck all-sky Comptonparameter map


Clusters of galaxies are the largest bound structures in the Universe. Thus, they are observablesof choice for cosmology both in terms of their aboundance and of their distribution on the sky.Clusters of galaxies can be observed at different wavelengths via their X-ray and radio emissionas well as from the optical emission of their galaxies. In addition, they can be studied via thethermal Sunyaev-Zeldovich (tSZ) effect, which is the distortion of the CMB spectrum caused bythe interaction of the CMB photons with the diffuse hot gas in the clusters.The Planck satellite, observing the sky at 9 frequencies from 30 to 857 GHz with a resoltuionfrom 40 to 4.5 arcmin, is particularly well adapted to the study of the tSZ effects in clusters ofgalaxies. Using dedicated component separation methods and by combining the Planck data at allfrequencies we have obtained the first all-sky map Compton parameter map of the tSZ emission.We present here a detailed characterisation of this map in terms of noise properties and systematics.We also present the angular power spectrum and non-gaussian properties of the map. Finally,these are used to obtain constraints on cosmological parameters. We find good agreement withthe results obtained from cluster number counts and in weak tension with CMB ones. We brieflyindicate how the latter can be understood in terms of cluster physics.

Primary author: Dr MACIAS-PEREZ, Juan Francisco (LPSC)

Presenter: Dr MACIAS-PEREZ, Juan Francisco (LPSC)



28th Texas Symp … / Report of Contributions Anisotropic Spherically Symmetri …


Anisotropic Spherically Symmetric Collapsing StarFrom Higher Order Derivative Gravity Theory


Combinations of Lovelock polynomials R2, RµνRµν and

RµνηδRµνηδ is added with

Einstein-Hilbert action to obtain interior metric of an anisotropicspherically symmetric collapsing (ASSC) stellar cloud. We assumethat time dependent interior metric of the ASSC cloud is flatMinkowski at beginning of the collapse. We solved linearized metricequation and obtained convergent series solutions for the interiormetric components, mass density, radial, transverse and isotropicpressures, time dependent barotropic index and dimensionlessanisotropic parameter. Ricci and Kretschmann scalars for oursolutions are not singular at the beginning and duration of thecollapse. Mathematical calculations predict that the collapsingcloud reach to its final state (compact object) and the collapsewill be stopped at a finite time tC . Also we obtain particulartimes tE and tA where the singularity and apparent horizon areformed. Singularity can not be observed by an external observerbecause of tE > tA > tC .

Primary author: Dr GHAFFARNEJAD, Hossein (Semnan University of IRAN)

Presenter: Dr GHAFFARNEJAD, Hossein (Semnan University of IRAN)



28th Texas Symp … / Report of Contributions ESA gravitational wave observator …


ESA gravitational wave observatory, eLISA and LISAPathfinder

Friday, December 18, 2015 9:00 AM (35 minutes)

The talk will likely take place during the cruise of LISA Pathfinder to its final interplanetary orbit.LISA Pathfinder is the technology precursor of the Gravitational Wave (GW) observatory that ESAintends to launch as their 3rd large size mission within the current planning.The talk will review the status and the scientific objectives of the GW observatory, and of itsreference mission eLISA, and will illustrate the instrumentation of LISA Pathfinder, its role withinESA’s GW program, and the expected scientific return of its upcoming operations.

Collaboration

LISA Pathfinder and eLISA

Primary author: Prof. VITALE, Stefano (University of Trento)

Presenter: Prof. VITALE, Stefano (University of Trento)



28th Texas Symp … / Report of Contributions Magnetars: the Universe strongest …


Magnetars: the Universe strongest magnetsThursday, December 17, 2015 11:50 AM (20 minutes)

Magnetars are a small subset of the neutron star population, being the strongest magnets we knowof. They show themselves via powerful X/gamma-ray steady and flaring emission. The energeticsof such flares in our Galaxy second only the supernova explosions. In this talk I will first reviewthe observational characteristics of these highly magnetic pulsars, and some recent discoveries inthe field. Subsequently, I will present what wecurrently know about their life-cycle, through detailed simulations of neutron star magneto-thermalevolution and pulsar population synthesis. I will then finish with some considerations on howthe study of the Galactic population of magnetars might constrain their possible connection withGamma Ray Bursts.

Collaboration

Nanda Rea (CSIC-IEEC/University of Amsetrdam)

Primary author: REA, Nanda (University of Amsterdam/CSIC-IEEC)

Presenter: REA, Nanda (University of Amsterdam/CSIC-IEEC)

Session Classification: IUPAP young astrophysicist awards


28th Texas Symp … / Report of Contributions CAFE: A relativistic Magnetohydr …


CAFE: A relativistic Magnetohydrodynamics codeThursday, December 17, 2015 4:15 PM (20 minutes)

We present CAFE, a code designed to solve the equations of relativistic ideal magnetohydrody-namics (RMHD) in three cartesian dimensions. We present the standard tests for the relativisticRMHD regime. The tests include among the two-dimensional (2D) and 3D tests with magneticfield. The code uses high-resolution shock-capturing methods, and we present the error analysisfor a combination that uses the Harten, Lax, van Leer, and Einfeldt flux formula combined with alinear, PPM and WENO5 reconstructors. We use the flux-constrained transport and the divergencecleaning methods to control the divergence-free magnetic field constraint.

Primary author: CRUZ OSORIO, Alejandro (Universidad Nacional Autónoma de México)

Co-author: LORA, Fabio (Universidad Industrial de Santander)

Presenter: CRUZ OSORIO, Alejandro (Universidad Nacional Autónoma de México)

Session Classification: 01 - Numerical relativity


28th Texas Symp … / Report of Contributions Relativistic pulsar winds: structur …


Relativistic pulsar winds: structure, shocks,reconnection.


Using the latest multi-wavelength observations of the inner-most regions of Crab nebular, we de-velop a model of relativistic pulsar winds that reproduces the detailed morphology of the Crabinner knot. We infer that a large equatorial sector of the wind, responsible for the production ofthe inner knot, is a low-magnetized flow - we see directly the surface of the termination shock.At intermediate polar angles the wind is highly magnetized. Using analytical and numerical ap-proaches we develop a model of explosive reconnection events in relativistic highly magnetizedpost-shock plasma, and apply the model to explain the Crab gamma-ray flares. Flares are producedduring explosive merger of macroscopic current-carrying magnetic flux tubes. During the mergersmall relative number of particles are accelerated to energies well above the average magneticenergy per particle.

Primary author: LYUTIKOV, Maxim

Presenter: LYUTIKOV, Maxim



28th Texas Symp … / Report of Contributions The gamma-ray Universe


The gamma-ray UniverseThursday, December 17, 2015 9:35 AM (35 minutes)

The last decade has marked a renaissance in the field of gamma-rayastronomy. Results from space and ground-based instruments, inparticular Fermi and the big three of ground-based gamma-rayastronomy: HESS, VERITAS and MAGIC, have transformed our view of thegamma-ray sky. The current datasets allow the very detailed study ofarchetypal particle accelerators across a very wide energy range forthe first time, and provide sufficient source counts to constrainpopulation/evolution models for a number of different sourceclasses. The recent results challenge many long-held assumptions inhigh energy astrophysics and there are also hints of new particlephysics. The richness of the results from these instruments provides astrong case for future instrumentation and with the HAWC detectorrecently completed, and the plans for CTA well advanced, the prospects forhighest energy photon astronomy over the next decade are extremely good.

Primary author: Prof. HINTON, Jim (Max Planck Institute for Nuclear Physics)

Presenter: Prof. HINTON, Jim (Max Planck Institute for Nuclear Physics)



28th Texas Symp … / Report of Contributions Exploring gravity in the strong fie …


Exploring gravity in the strong field regime withhigh throughput X-ray measurements


High-time-resolution and spectroscopic observations of accreting collapsed objects in the X-rayrange provide access to strong-field gravity, through measurements of the motions of matter or-biting a few gravitational radii away from black holes. Key predictions of strong field generalrelativity, such as relativistic epicyclic motions, precession, light bending and the presence andradius of an innermost stable circular orbit in the close vicinity of a black hole can be verified bymaking use of the two most important direct diagnostics, i.e. the relativistically broadened iron-lines and relativistic timescale variability, in particular the Quasi Periodic Oscillations. Both thelow and high curvature regimes of strong field gravity can be probed by studying supermassiveblack hole in Active Galactic Nuclei and stellar-mass black holes in X-ray Binaries, respectively.This will afford testing general relativity against those alternative theories of gravity which pre-dict deviations from General Relativity in the strong-field regime. To achieve these goals, verylarge area X-ray instrumentation with good spectral resolution is required. Prospects in this areaof research will be surveyed.

Primary author: Prof. STELLA, Luigi (INAF - Osservatorio Astronomico di Roma)

Presenter: Prof. STELLA, Luigi (INAF - Osservatorio Astronomico di Roma)



28th Texas Symp … / Report of Contributions Effects of the second-order vector …


Effects of the second-order vector mode on weaklensing signals


Vector mode of cosmological perturbation theory imprints characteristic signals on the weak lens-ing signals such as curl- and B-modes which are never imprinted by the scalar mode.However, the vector mode is neglected in the standard first-order cosmological perturbation the-ory since it only has a decaying mode.This situation changes if the cosmological perturbation theory is expanded up to second order.The second-order vector and tensor modes are inevitably induced by the product of the first-orderscalar modes.We study the effect of the second-order vector mode on the weak lensing curl- and B-modes.We find that the curl-mode induced by the second-order vector mode is comparable to that inducedby the primordial gravitational waves with the tensor-to-scalar ratio r = 0.1 at ℓ ≈ 200.In this case, the curl-mode induced by the second-order vector mode dominates at ℓ > 200.Furthermore, the B-mode cosmic shear induced by the second-order vector mode dominates onalmost all scales.However, we find that the observational signatures of the second-order vector and tensor modescannot exceed the expected noiseof ongoing and upcoming weak lensing measurements.We conclude that the curl- and B-modes induced by the second-order vector and tensor modes areunlikely to be detected in future experiments.

Primary author: Mr SAGA, Shohei (Naogya university)

Co-authors: Dr YAMAUCHI, Daisuke (The University of Tokyo); Dr ICHIKI, Kiyotomo (Nagoyauniversity)

Presenter: Mr SAGA, Shohei (Naogya university)

Session Classification: 12 - Gravitational lensing


28th Texas Symp … / Report of Contributions Is the Ni’s solution of the Tolman- …


Is the Ni’s solution of theTolman-Oppenheimer-Volkoff problem without themaximum-mass limit applicable to the real neutron

stars? A discussionTuesday, December 15, 2015 6:10 PM (3 minutes)

In 2011, Jun Ni published solution of the equations in the classical Tolman-Oppenheimer-Volkoff(TOV) modeling of spherically symmetric neutron star. The Ni’s solution implies no upper-masslimit and the outer surface of modeled object always appears to be above the event horizon. Infact, Ni found an infinite variety of sets of the TOV-problem solutions. The original Oppenheimer-Volkoff result provides only a single set from this variety offered by general relativity. As originallyOpenheimer and Volkoff as Ni assumed the positive energy density and pressure (or zero in thevacuum outside the object). And, the gravity of every mass element of the object had the attractivecharacter. Ni noted that this type of solution cannot be obtained in Newtonian physics. However,general relativity may not obey the limitations sourcing from the Newtonian gravity and, thus, itseems that the neutron-star models based on the Ni’s solution are still applicable on real compactobjets. We discuss the relevance of main objections against this applicability.

Primary author: Dr NESLUSAN, Lubos (Astronomical Institute, Slovak Academy of Sciences, 05960Tatranska Lomnica, Slovakia)

Presenter: Dr NESLUSAN, Lubos (Astronomical Institute, Slovak Academy of Sciences, 05960 Tatran-ska Lomnica, Slovakia)



28th Texas Symp … / Report of Contributions Cosmic ray acceleration and trans …


Cosmic ray acceleration and transportThursday, December 17, 2015 10:10 AM (35 minutes)

I will summarize the current understanding of the physical processes responsible for cosmic rayacceleration, mainly in supernova remnant shocks, and their transport in the interstellar medium.Special attention will be devoted to the comparison with most recent data of both multifrequencyemission from astrophysical sources and spectra of CRs measured locally.

Primary author: Prof. BLASI, Pasquale (INAF)

Presenter: Prof. BLASI, Pasquale (INAF)



28th Texas Symp … / Report of Contributions Un-Beamed Tidal Disruption Even …


Un-Beamed Tidal Disruption Events at Hard X-RaysTuesday, December 15, 2015 2:42 PM (20 minutes)

Thanks to their thermal emission, Tidal Disruption Events (TDEs) were detected regularly in thesoft X-rays and sometimes in the optical. Only few of them have been detected at hard X-rays:two are high redshift beamed events, one occurred at the core of a nearby galaxy and the last oneis of a different nature, involving a compact object in the Milky Way.The aims of presented work are to obtain a first sample of hard X-ray selected un-beamed TDEs,to determine their frequency and to probe if TDEs are usually or exceptionally emitting at hardX-rays.We performed extensive search for hard X-ray flares at the positions of over 53000 galaxies up to adistance of 100 Mpc in the Swift BAT archive. Light curves were extracted and parametrized. Thequiescent hard X-ray emission was used to exclude persistently active galactic nuclei. Significantflares from non-active galaxies were derived and checked for possible contamination.We found a sample of nine TDE candidates, which translates in a rate of 2× 10−5 galaxy−1 yr−1

above the BAT detection limit. This rate is consistent with these observed by XMM-Newton at softX-rays and in the optical from SDSS observations, and expected from simulations. We concludethat hard X-ray emission should be ubiquitous in un-beamed TDEs and that electrons should beaccelerated in their accretion flow.

Primary author: HRYNIEWICZ, Krzysztof (Nicolaus Copernicus Astronomical Centre)

Co-author: WALTER, Roland (University of Geneva)

Presenter: HRYNIEWICZ, Krzysztof (Nicolaus Copernicus Astronomical Centre)



28th Texas Symp … / Report of Contributions Broad-band properties of flat- …


Broad-band properties of flat-spectrum radio-loudnarrow-line Seyfert 1 galaxies


We studied a sample of 42 radio loud narrow-1ine Seyfert 1 galaxies (RLNLS1s) by using all theavailable multiwavelength observations and the information in literature. The masses of the cen-tral black holes are in the range ∼ 106−8M⊙, smaller than blazars, while the accretion luminosi-ties span from ∼ 0.01 to ∼ 0.49LEdd, with an outlier at 0.003, similarly to quasars. We detected90% of the sources in X-rays and 17% at γ rays. We found hourly variability at high energies.The study of the spectral energy distribution revealed dramatic spectral and flux changes in somesources, suggesting an interplay between the relativistic jet and the accretion disk. The calculatedjet power are within the interval 1042.6−45.6 erg s−1, generally lower than quasars and BL Lacobjects, but partially overlapping with the latter population. Once normalised by the black holemass, according to the theory by Heinz and Sunyaev (2003), the jet power of the three types ofAGN are consistent with each other. This indicates that, despite the observational differences, thecentral engine of RLNLS1s is quite similar to that of blazars. The historical difficulties in findingradio-loud narrow-line Seyfert 1 galaxies might be due to their low power and to intermittent jetactivity.

Reference: Foschini et al., 2015, A&A, 575, A13

Primary author: Dr FOSCHINI, Luigi (National Institute for Astrophysics - INAF)

Presenter: Dr FOSCHINI, Luigi (National Institute for Astrophysics - INAF)



28th Texas Symp … / Report of Contributions Axion as a cold dark matter candidate


Axion as a cold dark matter candidateWednesday, December 16, 2015 6:33 PM (3 minutes)

We show that the axion as a coherently oscillating scalar field acts as a cold dark matter (CDM) tothe second-order perturbations in all cosmological scales including the super-horizon scale. Theproof is made in the axion-comoving gauge. For a canonical mass, the axion pressure term causesdeviation from the CDM only on scales smaller than the Solar System size. Beyond such a smallscale the equations of the axion fluid are the same as the ones of the CDM based on the CDM-comoving gauge which are exactly identical to the Newtonian equations to the second order. Ouranalysis includes the cosmological constant, and can be easily applicable for the realistic situationincluding other fluids and fields.

Collaboration

Hyerim Noh, Jai-chan Hwang, Chan-Gyung Park

Primary author: NOH, Hyerim (Korea Astronomy and Space Science Institute)

Presenter: NOH, Hyerim (Korea Astronomy and Space Science Institute)

Session Classification: 05 - Dark matter


28th Texas Symp … / Report of Contributions Late-time cosmology with eLISA


Late-time cosmology with eLISAWednesday, December 16, 2015 4:15 PM (20 minutes)

In this talk I will consider the application of eLISA as a probe of the late-time cosmological expan-sion. In particular I will first review the concept of standard sirens and how these can be used toinvestigate the distant-to-redshift relation. I will then discuss the best strategies to obtain as manystandard sirens as possible, taking into account what kinds of electro-magnetic counterparts couldreasonably be detected and by which instruments. Finally, employing realistically simulated data,I will present the constraints we will be able to obtain on the cosmological parameters of Lamb-daCDM and dark energy models.

Primary author: TAMANINI, Nicola (CEA - France)

Co-authors: SESANA, Alberto (Birmingham University); CAPRINI, Chiara (CEA-Saclay); BA-RAUSSE, Enrico

Presenter: TAMANINI, Nicola (CEA - France)

Session Classification: 11 - Gravitational waves


28th Texas Symp … / Report of Contributions The Nexus Graviton, Dark Energy …


The Nexus Graviton, Dark Energy and Dark Matter

I present a novel approach to explaining the enigmas of the Dark Sector, late time cosmic ac-celeration and the Coincidence Problem via a self-consistent theory of Quantum Gravity calledNexus.Here we find that the graviton is not a messenger but rather a composite spin-2 particlethat induces constant rotational motion on any particle found in its radius of action. From thistheory one can derive the baryonic Tully - Fisher relation,calculate the value of the cosmologi-cal constant and the baryonic mass content of the observable universe. It also gives the quantumstates of space-time in the presence of baryonic matter as well as eliminate singularities from BlackHoles.

The peer reviewed paper can be freely downloaded here http://www.worldscientific.com/doi/abs/10.1142/S0219887815500425

Primary author: MARONGWE, Stuart

Presenter: MARONGWE, Stuart


28th Texas Symp … / Report of Contributions PICsar: Particle in Cell Pulsar Sim …


PICsar: Particle in Cell Pulsar SimulationsTuesday, December 15, 2015 5:15 PM (20 minutes)

We perform 2.5D axisymmetric simulations of the pulsar magnetosphere (aligned dipole rotator)using the charge conservative, relativistic, electromagnetic particle in cell code PICsar. The particlein cell method is a powerful tool for studying the pulsar magnetosphere, because it can handle theforce-free and vacuum limits as well as magnetic reconnection. In particular, dissipative regionsin the solution arise self-consistently, since we do not have any explicit dissipation in the code.

The structure of the electromagnetic fields in our simulations is on the whole consistent with theforce-free model, and the value of the spin-down luminosity is within ≈10% of the force-free value.However, a minimum of ≈15-20% (and as high as 50% depending on the plasma density at the lightcylinder) of the electromagnetic spin-down luminosity is transferred to the particles within fivelight cylinder radii. The energy is transferred to the particles most efficiently near the Y-point andcould potentially be radiated in the form of gamma rays. In the future, PIC codes could be used tobetter constrain the sites of gamma ray emission in the pulsar magnetosphere.

Primary author: BELYAEV, Mikhail (UC Berkeley/TAC)

Presenter: BELYAEV, Mikhail (UC Berkeley/TAC)



28th Texas Symp … / Report of Contributions Merger of binary neutron stars: G …


Merger of binary neutron stars: Gravitational wavesand mass ejection


The merger of binary neutron stars is one of the most promising gravitational wave sources. Forthe detection of gravitational waves, numerical relativists are required to accurately predict grav-itational waveforms and possible electromagnetic signals. I will talk on our latests effort for thenumerical-relativity simulations: magnetohydrodynamics and radiation hydrodynamics simula-tions.

Primary author: SHIBATA, Masaru (Kyoto University)

Presenter: SHIBATA, Masaru (Kyoto University)



28th Texas Symp … / Report of Contributions General-relativistic pulsars magne …


General-relativistic pulsars magnetospheresTuesday, December 15, 2015 4:35 PM (20 minutes)

Pulsar magnetospheres are shaped by ultra-relativistic electron/positron plasmas flowing in astrong magnetic field and subject to strong gravitational fields. The former induces magneto-spheric currents and space charges responsible for the distortion of the electromagnetic field basedon pure electrodynamics. The latter induces other perturbations in these fields based on space-timecurvature. The force-free approximation describes the response of this magnetosphere to the pres-ence of currents and charges and has been investigated by many authors. In this context, generalrelativity has been less discussed to quantify its influence on the neutron star electrodynamics. Itis the purpose of this paper to compute general-relativistic force-free pulsar magnetospheres forrealistic magnetic field configurations such as the inclined dipole. We performed time-dependentsimulations of Maxwell equations in the 3+1 formalism of a stationary background metric in theslow-rotation approximation. We computed the resulting Poynting flux depending on the ratioR/rL and on frame-dragging through the spin parameter as. Both effects act together to increasethe total Poynting flux seen by a distant observer by a factor of a few. Moreover we retrieve thesin^2 chi dependence of this luminosity, chi being the obliquity of the pulsar, as well as a brakingindex close to n=3.

Primary author: PÉTRI, Jérôme (Université de Strasbourg)

Presenter: PÉTRI, Jérôme (Université de Strasbourg)



28th Texas Symp … / Report of Contributions Effect of geodetic precession on th …


Effect of geodetic precession on the evolution ofpulsar high-energy pulse profiles as derived with the

striped-wind model.Tuesday, December 15, 2015 5:35 PM (20 minutes)

Geodetic precession has been observed directly in the double-pulsar PSR J0737-3039. Its rate haseven been measured and agrees with predictions of general relativity. Very recently, the doublepulsar has been detected in X-rays and gamma-rays. This fuels the hope observing geodetic pre-cession in its high-energy pulse profile. Unfortunately, the geometric configuration of the binaryrenders any detection of such an effect unlikely. Nevertheless, this precession is present in otherrelativistic binaries or double neutron star systems containing at least one X-ray or gamma-ray pul-sar. We compute the variation of the high-energy pulse profile expected from this geodetic motionaccording to the striped-wind model. We compare our results with two-pole caustic and outer gapemission patterns. For a sufficient misalignment between the orbital angular momentum and thespin angular momentum, a significant change in the pulse profile as a result of geodetic precessionis expected in X-rays and gamma-rays. The essential features of the striped wind is summarized inseveral plots showing the evolution of the maximum of the pulsed intensity, the separation of bothpeaks, if present, and the variation in the width of each peak. We highlight the main differenceswith other competing high-energy models. Some predictions about possible future detection ofhigh-energy emission from double neutron star systems with the highest spin precession rate aremade. Such observations will definitely favor some pulsed high-energy emission scenarios.





28th Texas Symp … / Report of Contributions Multipolar electromagnetic fields a …


Multipolar electromagnetic fields around neutronstars: exact vacuum solutions and related properties.


The magnetic field topology in the surrounding of neutron stars is one of the key questions in pul-sar magnetospheric physics. A very extensive literature exists about the assumption of a dipolarmagnetic field but very little progress has been made in attempts to include multipolar compo-nents in a self-consistent way. In this talk, we study the effect of multipolar electromagnetic fieldsanchored in the star. We give exact analytical solutions in closed form for any order~l and applythem to the retarded point quadrupole~(l=2), hexapole~(l=3) and octopole~(l=4), a generalizationof the retarded point dipole~(l=1). We also compare the Poynting flux from each multipole andshow that the spin down luminosity depends on the ratio R/rL, R being the neutron star radiusand rL the light-cylinder radius. Therefore the braking index also depends on R/rL. As such multi-pole fields possess very different topology, most importantly smaller length scales compared to thedipolar field, especially close to the neutron star, we investigate the deformation of the polar capinduced by these multipolar fields. Such fields could have a strong impact on the interpretation ofthe pulsed radio emission suspected to emanate from these polar caps as well as on the inferredgeometry deduced from the high-energy light-curve fitting. Discrepancies between the two-polecaustic model and our new multipole-caustic model are emphasized with the quadrupole field. Tothis respect, we demonstrate that working with only a dipole field can be very misleading.





28th Texas Symp … / Report of Contributions GRB polarization with the POLAR …


GRB polarization with the POLAR detector.Monday, December 14, 2015 3:24 PM (21 minutes)

The POLAR detector will be launched together with the Tiangong 2Chinese space station in the Summer of 2016 from Jiuquan Launch center.POLAR is a GRB polarimeter that will be able to measure GRB polarizationdegree with 10% precision for 10 GRB per year. POLAR detector has been build by aChinese-Swiss-Polish collaboration.POLAR flight spare model has passed allqualification tests during 2014 and was tested and calibrated in a polarizedbeam facility in ESRF Grenoble. POLAR flight modelhas passed all acceptation leveltests and was delivered to China in July 2015 for integration on Tiangong 2.GRB polarization measurements will help to validate or infirm thepredictions of the different models of the GRB central engine.GRB polarization measurements are also interesting asprobe of the quantum gravitation effects. POLAR can also be used to performsome Solar flare polarization measurements.

Collaboration

The POLAR collaboration

Primary author: Dr PRODUIT, Nicolas (Universite de Geneve (CH))

Presenter: Dr PRODUIT, Nicolas (Universite de Geneve (CH))

Session Classification: 13 - Gamma-ray bursts


28th Texas Symp … / Report of Contributions How the observational quantities o …


How the observational quantities of stronggravitational lens effect depend on BH’s mass and

spinThursday, December 17, 2015 2:00 PM (21 minutes)

According to the general relativity (GR), the black hole (BH) is characterized by three parameters:mass M , spin angular momentum J and electric charge Q.In real cases, the charge is expected to be zero, Q = 0.Then, the “BH observation” may be understood as the measurement of M and J through a directobservation of GR phenomena, for example the strong gravitational lens effect.I am studying how the two parameters (M,J) appear in a time series data (light curve) seen bysingle telescope observing the strong gravitational lens effect by Kerr BH.The situation treated in my study consists of three parts as follows:

(1) If an emission of light with short duration (burst-like emission) occurs near a BH, we focus ontwo light rays:One light ray propagates from the source to observer along the shortest path which does not windaround the BH (”direct ray” or “zero-winding ray”).Another ray propagates along the secondary short path which winds once around the BH (”sec-ondary ray” or “1-winding ray”).

(2) When the observer detects the 0-winding and 1-winding rays by single telescope, he/she can (inprinciple) readout following two informations from the light curve seen by the telescope: the timedelay ∆tobs between detection time of 0-winding and 1-winding rays, and the ratio of brightnessRobs of 0-winding and 1-winding rays.

(3) These two parameters (∆tobs, Robs) are determined by BH parameters (M,J) and also theposition and velocity (x, v) of source at the emission.

I will report how these quantities (M,J, x, v) determine the two observational quantities (∆tobs, Robs).Also, it will be found that the estimated values of ∆tobs and Robs seem to be detectable by thepresent telescope capability.

Primary author: SAIDA, Hiromi (Daido University)

Presenter: SAIDA, Hiromi (Daido University)



28th Texas Symp … / Report of Contributions Three dimensional global General …


Three dimensional global General RelativisticRadiative Magnetohydrodynamical simulations to

test stability of thin disk around black holeThursday, December 17, 2015 4:36 PM (21 minutes)

The stability of geometrically thin radiation pressure dominated accretion disks around black holesremained under debate. Analytical work concludes that such disks should be thermally unstable.Newtonian shearing box simulations in the past show that these disks may be thermally stable.In last few years other pseudo-Newtonian shearing box simulations showed that the disks arethermally unstable. So basic question arises what is actual fate of the geometrically thin radiationpressure dominated accretion disk ? In order to give better understanding we first time performedthree dimensional global General Relativistic Radiative Magnetohydrodynamical (3D GRRMHD)simulations of geometrically thin and radiation pressure dominated accretion disks around blackhole. We found that indeed radiation pressure dominated geometrically thin disks are thermallyunstable. We treated the disk as optically thick to have strong interaction with radiation.

Collaboration

Mishra, B.; Fragile, P.C; Johnson, C.L.; Kluzniak W.

Primary author: MISHRA, Bhupendra (Nicolaus Copernicus Astronomical Center Warsaw Poland)

Presenter: MISHRA, Bhupendra (Nicolaus Copernicus Astronomical Center Warsaw Poland)



28th Texas Symp … / Report of Contributions MAGIC latest results


MAGIC latest resultsWednesday, December 16, 2015 2:25 PM (25 minutes)

MAGIC is a ground-based astrophysics instrument for measuring gamma rays in the energy range~ 35 GeV - 50 TeV. It is the first instrument paving the road into the sub-100 GeV gamma-ray sky.MAGIC consists of two 17m diameter, F/1.03 imaging atmospheric Cherenkov telescopes, whichare separated by 85m distance and are located at 2200m a.s.l. in the Roque de los Muchachos Euro-pean North Observatory on the Canary island of La Palma. This talk will provide a review of themost important results recently obtained by the MAGIC collaboration. They include a substantiallist of flaring episodes detected from AGN, leading to the discovery of VHE emission from redshiftclose to 1 and constraints on the EBL. In our galaxy, MAGIC measured the spectrum of gamma-rays from the Crab pulsar extending from few tens of GeV to above 1 TeV. Deep observations tosearch for dark matter as well as other results on fundamental physics will also be reported.

Collaboration

MAGIC Collaboration

Primary author: BLANCH, Oscar (IFAE)

Presenter: BLANCH, Oscar (IFAE)

Session Classification: 19 - VHE & CR


28th Texas Symp … / Report of Contributions Where are the baryons?


Where are the baryons?Thursday, December 17, 2015 4:15 PM (20 minutes)

In the local Universe, about half of the total baryon content of the Universe is still escaping ourcensus. Understanding the state and distribution of these missing baryons is a major questionfor our knowledge of galaxy evolution and cosmology. Numerical simulations predict that themissing baryons should be in the form of a very diffuse, warm-hot (T~1e5-1e7 K) state, whichwould remain largely undetected both inside dark-matter halos and in the filaments of the cosmicweb. I will present recent results on the hunt for the missing baryons. First, I will present acombined X-ray and gravitational lensing study of filaments in the outskirts of a massive galaxycluster, which unveil the baryon content of intergalactic filaments. I will also show the results ofsystematic studies of the global baryon budget of massive halos in the XXL and CFHTLS surveys.These measurements will be combined to update our knowledge of the Universe’s missing baryons.

Primary author: Dr ECKERT, Dominique (University of Geneva)

Presenter: Dr ECKERT, Dominique (University of Geneva)



28th Texas Symp … / Report of Contributions Real-Time Evolution Of Relativisti …


Real-Time Evolution Of Relativistic Jets InMicroquasars

Wednesday, December 16, 2015 5:17 PM (21 minutes)

Jets appear in Astrophysics in very different environments and scales across the Universe, andthey seem to share common features in all cases. Their study can then help us to understand awidespread outflow mechanism. However, their large-scale dynamics remain hidden to observa-tion along human time scales because they usually develop too slowly, either because of their largesizes (in active galactic nuclei), or because of their slow velocities (in Herbie-Haro objects). How-ever, microquasars combine both relatively short extensions and relativistic velocities, giving usthe chance to better study the jet evolution and interaction with their environments in almost realtime. Here we present, for the first time, an observational proof of such large-scale morphologicalchanges in the case of GRS 1758-258. Archival radio observations have been used to conform a setof photograms of the evolution of such microquasar throughout two decades, confirming its struc-tural variations that may be related to hydrodynamical instabilities. In addition, we have studiedthe prototypical microquasar 1E 1740.7-2942 in radio wavelengths to find out again changes in thejet morphology, that seem to be mainly originated by precession in this case. These results let us toconfirm their up-to-now disputed Galactic nature and provide a benchmark for testing theoreticalmodels accounting for relativistic jets dynamics and their interactions with the medium.

Primary author: Dr LUQUE-ESCAMILLA, Pedro Luis (Universidad de Jaén)

Co-authors: Dr ROMERO, Gustavo (Instituto Argentino de Radioastronomía, C.C.5, 1894 Villa Elisa,Buenos Aires, Argentina); Dr MARTÍ-RIBAS, Josep (Universidad de Jaén); Dr MARTÍNEZ-AROZA,José (Universidad de Granada); Dr SÁNCHEZ-SUTIL, Juan Ramón (Research Group FQM-322); DrMUÑOZ-ARJONILLA, Álvaro (Research Group FQM-322)

Presenter: Dr LUQUE-ESCAMILLA, Pedro Luis (Universidad de Jaén)



28th Texas Symp … / Report of Contributions General Relativity and Cosmic Str …


General Relativity and Cosmic Structure FormationMonday, December 14, 2015 4:35 PM (20 minutes)

The Newtonian approximation which is usually invoked in N-body simulations of cosmic largescale structure relies on the assumptions that gravitational fields are weak and that they are onlysourced by nonrelativistic matter. The latter constitutes an implicit assumption about the natureof the “dark” components of the Universe (dark matter and dark energy), thereby precluding aserious assessment of some potentially interesting models. Here we present the first N-body sim-ulations of cosmic structure formation based on a weak field approximation to General Relativity,taking into account all six degrees of freedom of the metric. The geodesic equations are solvedconsistently also for relativistic particles, such as massive neutrinos. Our approach is very generaland can be applied to various settings where the Newtonian approximation would be unreliableor inconsistent, for instance some models of dynamical dark energy or modified gravity.

Primary authors: ADAMEK, Julian (Université de Genève); KUNZ, Martin (Universite de Geneve(CH)); DURRER, Ruth (University of Geneva)

Presenter: ADAMEK, Julian (Université de Genève)

Session Classification: 07 - Large scale structures


28th Texas Symp … / Report of Contributions Disrupted globular clusters explai …


Disrupted globular clusters explain gamma rayexcess in the Galactic center


The Fermi satellite has recently detected gamma ray emission from the central regions of ourGalaxy. This may be evidence for dark matter particles, a major component of the standard cos-mological model, annihilating to produce high-energy photons. We show that the observed signalmay instead be generated by millisecond pulsars that formed in dense star clusters in the Galac-tic halo. Most of these clusters were ultimately disrupted by evaporation and gravitational tides,contributing to a spherical bulge of stars and stellar remnants.

Primary authors: Prof. KOCSIS, Bence (Eötvös University); Dr BRANDT, Timothy (Institute forAdvanced Study)

Presenter: Prof. KOCSIS, Bence (Eötvös University)

Session Classification: 17 - Activity at the galactic center


28th Texas Symp … / Report of Contributions Direct formation of supermassive …


Direct formation of supermassive black holes; frommergers of protogalaxies to global relativistic

collapseTuesday, December 15, 2015 5:00 PM (20 minutes)

We present the latest developments of the merger-driven scenario for supermassive black holeformation originally developed in Mayer et al. (2010,Nature, 466. 1082). We show how including realistic radiation physics in mergers of protogalaxiesdriven from cosmological initial conditions strengthens the proposal that supermassive nuclearclouds may form in only a few 10^8 yr in the nucleus of the remnant, as a result of supersonicturbulence hampering fragmentation and normal star formation even in the presence of metal-enriched gas. The billion solar mass clouds can lead to a supermassive star, which can rapidlyproduce a massive black hole seed (M_BH > 10^5 Mo), or can undergo a “dark collapse” all theway into a supermassive black hole via the relativistic radial instability depending on the residualangular momentum (Mayer et al. 2015, ApJ, in press).Both scenarios explain naturally the rapid emergence of high-z QSOs at z > 6. Finally, unprece-dented 3D computations joining for the first time galaxy formation simulations in a cosmologicalcontext with relativistic hydro calculations of supermassive cloud collapse, including even theeffect of nuclear burning in metal-enriched gas, will be presented and the preliminary results dis-cussed in light of the “dark collapse” scenario.

Collaboration

Lucio Mayer, Davide Fiacconi (University of Zurich), Pedro Montero (MPA Garching)

Primary author: Prof. MAYER, Lucio (University of Zurich)

Presenter: Prof. MAYER, Lucio (University of Zurich)



28th Texas Symp … / Report of Contributions Modeling Bright Gamma-ray and R …


Modeling Bright Gamma-ray and Radio Emissionfrom Fast Cloud Shocks at Middle-aged SNRs


Recent observations by the Large Area Telescope (LAT) onboard the Fermi satellite have revealedbright gamma-ray emission from middle-aged supernova remnants (SNRs) inside our Galaxy. Theseremnants which also possess bright non-thermal radio shells are often found to be interacting di-rectly with surrounding gas clouds. We explore the non-thermal emission mechanism at thesedynamically evolved SNRs by constructing a hydrodynamical model. Two scenarios of particleacceleration, eithera re-acceleration of Galactic cosmic rays (CRs) or an efficient nonlinear diffusive shock accelera-tion (NLDSA) of particles injected from downstream, are considered. Using parameters inferredfrom observations, our models are contrasted with the observed spectra of SNR W44. For there-acceleration case, we predict a significant enhancement of radio and GeV emission as the SNRundergoes a tran-situation into the radiative phase. If sufficiently strong magnetic turbulence is present in the molec-ular cloud, the re-acceleration scenario can explain the observed broadband spectral properties.The NLDSA scenario also succeeds in explaining the gamma-ray spectrum but fails to reproducethe radio spectral index. Efficient NLDSA also results in a significant post-shock CR pressure thatlimits the cooling compression and prevents the formation of a prominent dense shell. Some otherinteresting differences between the two models in hydrodynamical behavior and resulting spectralfeatures are illustrated in detail.

Primary author: Dr LEE, Shiu Hang (Herman) (ISAS/JAXA)

Co-authors: Dr PATNAUDE, Daniel (SAO); Prof. ELLISON, Donald (North Carolina State Uni-vesity); Dr RAYMOND, John (CfA); Dr SLANE, Patrick (SAO); Dr NAGATAKI, Shigehiro (RIKEN)

Presenter: Dr LEE, Shiu Hang (Herman) (ISAS/JAXA)



28th Texas Symp … / Report of Contributions Relativistic effects and primordial …


Relativistic effects and primordial non-Gaussianityin the matter density fluctuation


We present the third-order analytic solution of the matter density fluctuation in the proper-timehypersurface of nonrelativistic matter flows by solving the nonlinear general relativistic equations.The proper-time hypersurface provides a coordinate system that a local observer can set up with-out knowledge beyond its neighborhood, along with physical connections to the local Newtoniandescriptions in the relativistic context. The initial condition of our analytic solution is set up bythe curvature perturbation in the comoving gauge, clarifying its impact on the nonlinear evolution.We compute the effective non-Gaussian parameters due to the nonlinearity in the relativistic equa-tions. With proper coordinate rescaling, we show that gravity respects the equivalence principlethe equivalence principle is respected and the relativistic effect vanishes in the large-scale limit.

Primary author: YOO, Jaiyul (University of Zurich)

Presenter: YOO, Jaiyul (University of Zurich)



28th Texas Symp … / Report of Contributions Dark matter detection - an experi …


Dark matter detection - an experimental overviewTuesday, December 15, 2015 9:35 AM (35 minutes)

A major challenge of modern physics is to decipher the nature of dark matter. Astrophysical ob-servations provide ample evidence for the existence of an invisible and dominant mass componentin the observable universe, from the scales of galaxies up to the largest cosmological scales. Thedark matter could be made of new, yet undiscovered elementary particles, with allowed massesand interaction strengths with normal matter spanning an enormous range. Axions, producednon-thermally in the early universe, and weakly interacting massive particles (WIMPs), whichfroze out of thermal equilibrium with a relic density matching the observations, represent twowell-motivated, generic classes of dark matter candidates. Dark matter axions could be detectedby exploiting their predicted coupling to two photons, where the highest sensitivity is reached byexperiments using a microwave cavity permeated by a strong magnetic field. WIMPs could be di-rectly observed via scatters off atomic nuclei in underground, ultra low-background detectors, orindirectly, via secondary radiation produced when they pair annihilate. They could also be gener-ated at particle colliders such as the LHC, where associated particles produced in the same processare to be detected. After a brief introduction to the phenomenology of particle dark matter detec-tion, I will discuss the most promising experimental techniques to search for axions and WIMPs,addressing their current and future science reach, as well as their complementarity.

Primary author: Prof. BAUDIS, Laura (University of Zurich)

Presenter: Prof. BAUDIS, Laura (University of Zurich)



28th Texas Symp … / Report of Contributions An External Shock Origin of GRB …


An External Shock Origin of GRB 141028AMonday, December 14, 2015 4:55 PM (20 minutes)

The prompt emission of the long, smooth, and single-pulsed gamma-rayburst, GRB 141028A, is analyzed under the guise of anexternal shock model. First, we fit the gamma-ray spectrum with atwo-component photon model, namely synchrotron+blackbody, and thenfit the recovered evolution of the synchrotron vFv peak to ananalytic model derived considering the emission of a relativisticblast-wave expanding into an external medium. The prediction of themodel for the vFv peak evolution matches well with theobservations. We observe the blast-wave transitioning into thedeceleration phase. Further we assume the expansion of theblast-wave to be nearly adiabatic, motivated by the low magneticfield deduced from the observations. This allows us to recoverwithin an order of magnitude the flux density at the vFv peak,which is remarkable considering the simplicity of the analyticmodel. Under this scenario we argue that the distinction betweenprompt and afterglow emission is superfluous asboth early and late time emission emanate from the same source.While the external shock model is clearly not a universal solution,this analysis opens the possibility that at least some fraction ofGRBs can be explained with an external shock origin of their promptphase.

Collaboration

Damine Bèguè

Primary author: Dr BURGESS, J. Michael (KTH Royal Institute of Technology)

Co-author: Dr BÈGUÈ, Damien (KTH Royal Institute of Technology)

Presenter: Dr BURGESS, J. Michael (KTH Royal Institute of Technology)



28th Texas Symp … / Report of Contributions Beyond General Relativity: The G …


Beyond General Relativity: The GeometricDeformation and New Black Hole Solutions


In the context of extra-dimensional gravity, as the Randall-Sundrum brane-world, a consistentextension of the minimal geometric deformation approach (MGD) is used to study the exteriorspacetimearound spherically symmetric self-gravitating system. A modified Schwarzschild geometry is ob-tained and new black hole solutions are shown. A possible extension of this approach in F (R)

theories is also presented.

Primary author: OVALLE, Jorge (Simon Bolivar University)

Presenter: OVALLE, Jorge (Simon Bolivar University)



28th Texas Symp … / Report of Contributions Solving the Einstein-Maxwell Equ …


Solving the Einstein-Maxwell Equations for theDispersive Propagation of Light during Mixmaster

Kasner Epochs and other Anisotropic Early-UniverseModels


The pre-homogenized very early universe generically experiences Mixmaster-like behavior as it ap-proaches the Big Bang, featuring a sequence of anisotropically expanding Kasner epochs. Beyonddrawing general conclusions about the transport of mass-energy in such environments, it wouldbe helpful to obtain as much information as possible about the detailed propagation of energy inrapidly and nonadiabatically expanding metrics for which the geometrical optics approximationsubstantially breaks down. Here we solve for the propagation of (“test particle”) electromagneticfields through background spacetimes with various sets of Kasner expansion indices. In solving theEinstein-Maxwell equations, we obtain independent fourth-order differential equations for each ofthe electric and magnetic fields which can be individually solved for the amplitudes and phase ve-locities of the fields to yield interesting information about how they are parametrically drivenby the asymmetrically expanding early universe. Furthermore, we consider other anisotropic(and non-vacuum) models, including metrics related to the Vaidya and Szekeres-Szafron solutions,which include inhomogeneity as well as anisotropy.

Primary author: BOCHNER, Brett (Hofstra University)

Presenter: BOCHNER, Brett (Hofstra University)

Session Classification: 02 - Exact solutions


28th Texas Symp … / Report of Contributions Tracing dark energy with quasars.


Tracing dark energy with quasars.Monday, December 14, 2015 2:27 PM (26 minutes)

The discovery of the accelerated expansion of the Universe lead to the concept of dark energy. Thisis one of the most interesting topic in modern relativistic astrophysics. Precise measurement ofthis effect is a key to understand the nature of this medium, and we need good probes to do that.Quasars appears as an ideal candidate for this purpose as these objects are highly luminous anddetected in wide range of redshift (0< z <7). They can be used to track the history of the expansionof the Universe (Watson et al. 2011, Czerny et al. 2013, Marziani & Sulentic 2013, 2014; Wang et al.2013; Hoenig 2014; Yoshii et al.2014). I will describe new encouraging results from the dedicatedspectroscopic monitoring being currently performed by our team using Mg II line.

Quasars are not standard candles so their use is based on determination of their two parametersredshifts and, independently, absolute luminosities. Absolute luminosity, combined with the ob-served luminosity, allows to obtain the luminosity distance to an individual quasar. Thus for eachsource we have independently the distance and the velocity (from redshift), i.e. the Universe ex-pansion rate. The method is essentially equivalent to the use of the SN Ia but it is important tohave several independent tracers as each of them have specific, hard to estimate, systematic errors.Specific advantage of quasars is, they do not show significant evolution of their properties withredshift which is likely a serious problem for SN Ia. The project in which I am involved uses the in-termediate redshift quasars observed with 11-m Southern African Large Telescope. Determinationof the quasar absolute luminosity comes from the measurement of the time delay between one ofthe strong emission lines and a continuum. MgII line is suitable for sources with redshift between0.4 and 1.5, where this strong line moves to optical band of the spectrum. High-quality spectrafrom SALT allow for a very detailed modeling of the line shape and remove potential sources of thesystematic errors. I will summarize all pros and cons of various recently proposed quasar-basedmethods of the measurement of the dark energy content of the Universe.

Collaboration

B. Czerny, M. Bilicki, K. Hryniewicz, M. Krupa, A. Kurcz, P. Marziani, A. Pollo, W. Pych, A. Udalski

Primary author: ŚREDZIŃSKA, Justyna (Nicolaus Copernicus Astronomical Center PAS)

Co-author: Prof. CZERNY, Bożena (Center for Theoretical Physics PAS, Warsaw, Poland)

Presenter: ŚREDZIŃSKA, Justyna (Nicolaus Copernicus Astronomical Center PAS)

28th Texas Symp … / Report of Contributions Orbital resolved spectroscopy of G …


Orbital resolved spectroscopy of GX 301-2 with MAXIMonday, December 14, 2015 5:45 PM (20 minutes)

GX 301-2, a bright high-mass X-ray binary with an orbital period of 41.5 days, exhibits stable pe-riodic orbital intensity modulations with a strong pre-periastron X-ray flare. Several models havebeen proposed to explain the accretion at different orbital phases, invoking accretion via stellarwind, equatorial disc, and accretion stream from the companion star. We present results from ex-haustive orbital phase resolved spectroscopic measurements of GX 301-2 using data from the GasSlit Camera onboard MAXI. Using spectroscopic analysis of the MAXI data with unprecedentedorbital coverage for many orbits continuously, we have found a strong orbital dependence of theabsorption column density and equivalent width of the iron emission line. A very large equiv-alent width of the iron line along with a small value of the column density in the orbital phaserange 0.10–0.30 after the periastron passage indicates the presence of high density absorbing mat-ter behind the neutron star in this orbital phase range. A low energy excess is also found in thespectrum at orbital phases around the pre-periastron X-ray flare. The orbital dependence of theseparameters are then used to examine the various models aboutmode of accretion on to the neutron star in GX 301-2.

Primary author: Ms ISLAM, Nazma (Indian Institute of Science, Raman Research Institute, Banga-lore, India)

Co-author: Dr PAUL, Biswajit (Raman Research Institute, Bangalore, India)

Presenter: Ms ISLAM, Nazma (Indian Institute of Science, Raman Research Institute, Bangalore,India)



28th Texas Symp … / Report of Contributions Orbital evolution and search for ec …


Orbital evolution and search for eccentricity andapsidal motion in the eclipsing HMXB 4U 1700–37


In the absence of detectable pulsations in the eclipsing High Mass X-ray binary 4U 1700–37, theorbital period decay is necessarily determined from the eclipse timing measurements. We haveused the earlier reported mid-eclipse time measurements of 4U 1700–37 together with new mea-surements from long term light curves obtained with the all sky monitors RXTE–ASM, Swift–BATand MAXI–GSC, as well as observations with RXTE–PCA, to measure the long term orbital evolu-tion of this binary. The orbital period decay rate of the system is estimated to be ‘P/P = −(4.7 ± 1.9)× 10^−7 yr^−1 , smaller compared to its previous estimates. We have also used the mid-eclipsetimes and the eclipse duration measurements obtained from 10 years long X-ray light curve ob-tained with Swift–BAT to separately put constraints on the eccentricity of the binary system andattempted to measure any apsidal motion. For a reasonable rate of apsidal motion for this binarysystem, the eccentricity is found to be less than 0.008, which limits our ability to determine theapsidal motion rate from the current data. We discuss the discrepancy of the current limit of ec-centricity with the earlier reported values from radial velocity measurements of the companionstar.

Primary author: Ms ISLAM, Nazma (Indian Institute of Science, Raman Research Institute, In-dia)

Co-author: Dr PAUL, Biswajit (Raman Research Institute, Bangalore, India)

Presenter: Ms ISLAM, Nazma (Indian Institute of Science, Raman Research Institute, India)



28th Texas Symp … / Report of Contributions Mildly obscured active galaxies an …


Mildly obscured active galaxies and the diffuse X-raybackground


The diffuse cosmic X-ray background1 (CXB) is the sum of the emission of discrete sources, mostlymassive black-holes accreting matter in active galactic nuclei (AGN)2. The CXB spectrum differsfrom the integration of the spectra of individual sources, calling for a large population, undetectedso far, of strongly obscured Compton thick AGN3. Such objects are predicted by unified models4,which attribute most of the AGN diversity to their inclination on the line of sight, and play an im-portant role for the understanding of the growth of black holes5 in the early Universe. The fractionof obscured AGN at low redshift can be derived from the observed CXB spectrum assuming AGNspectral templates and luminosity functions. Here we show that high signal-to-noise average hardX-ray spectra, derived from more than a billion seconds of effective exposure with the Swift/BATinstrument6, imply that mildly obscured Compton thin AGN feature a strong reflection and con-tribute massively to the CXB. A population of Compton thick AGN larger than that effectivelyobserved is not required, as no more than 8% of the CXB flux can be attributed to them. Strongerreflection in mildly obscured AGN suggests that the covering fraction of the gas and dust surround-ing their central engines is a key factor in shaping their appearance. These mildly obscured AGNare easier to study at high redshift than Compton thick sources.

Primary author: ESPOSITO, Valentino


Presenter: ESPOSITO, Valentino



28th Texas Symp … / Report of Contributions The high energy spectrum of 3C 273


The high energy spectrum of 3C 273Tuesday, December 15, 2015 6:26 PM (3 minutes)

The high energy spectrum of 3C 273 is usually understood in terms of inverse-Compton emissionin a relativistic leptonic jet.This model predicts variability patterns and delays that could be tested with simultaneous obser-vations from the radio to the GeV range. The instruments IBIS, SPI, JEM-X on board INTEGRAL,PCA on board RXTE, and LAT on board Fermi have enough sensitivity to follow the spectral vari-ability of 3C 273 from the keV to the GeV. We looked for correlations between the different energybands, including radio data at 37 GHz collected at the Metsähovi Radio Observatory and built quasi-simultaneous multiwavelength spectra in the high energy domain when the source is flaring eitherin the X-rays or in the γ rays.Both temporal and spectral analysis suggest a two-component model to explain the complete highenergy spectrum. X-ray emission is likely dominated by a Seyfert-like component while the γ-rayemission is dominated by a blazar-like component produced by the relativistic jet. The variabilityof the blazar-like component is discussed, comparing the spectral parameters in the two differentspectral states. Changes of the electron Lorentz factor are found to be the most likely source ofthe observed variability.

Primary author: ESPOSITO, Valentino

Co-authors: TRAMACERE, Andrea (ISDC); LÄHTEENMÄKI, Anne (Aalto University); TÜRLER,Marc (ISDC); TORNIKOSKI, Merja (Aalto University); JEAN, Pierre (Université de Toulouse); WALTER,Roland (University of Geneva)

Presenter: ESPOSITO, Valentino



28th Texas Symp … / Report of Contributions Neutrino masses and cosmology w …


Neutrino masses and cosmology with Lyman-alphaforest power spectrum


I will present the constraint on massive neutrinos that was obtained recently using Lyman-alphaforest, BAO and CMB data. I will first describe the measurement of the power spectrum in theLyman-alpha forest observed in quasars of the SDSS/BOSS survey. I will then present the extensivesuite of N-body/hydro simulations that has been developed specifically for the purpose of thisstudy, and show how it can be used to place constraints on the sum of the neutrino masses atthe level of 0.12 eV (95% confidence level). I will also discuss the impact of Ly-alpha forest on themeasurement of the primordial fluctuations by CMB experiments. Finally, I will illustrate howthese data and simulations can also constrain the mass of neutrinos considered as Warm DarkMatter.

Collaboration

SDSS/BOSS

Primary author: YECHE, Christophe

Co-author: PALANQUE-DELABROUILLE, Nathalie (CEA)

Presenter: YECHE, Christophe

Session Classification: 09 - Cosmic neutrinos


28th Texas Symp … / Report of Contributions Quantum effects on black holes: e …


Quantum effects on black holes: evaporation,tunnelling, information leak. Anything observable?


Black holes are well understood in their classical dynamics or as background geometry for quan-tum fields. But their quantum gravitational properties remain elusive. These are crucial to under-stand what happens to the matter falling inside, and to know the holes’ long term stability. Thereare a number of recent results and ideas on this issue, including the firewall theorem, Planck stars,graviton condensate approximations and others. There have also been suggestions for possibleobservable windows, for instance effects of metric fluctuations outside the horizon, or cosmic raysfrom by primordial black holes’ decay.

Primary author: Prof. ROVELLI, Carlo (Université de la Méditerranée, Marseille)

Presenter: Prof. ROVELLI, Carlo (Université de la Méditerranée, Marseille)



28th Texas Symp … / Report of Contributions Shedding light on the early Univer …


Shedding light on the early Universe with THESEUSMonday, December 14, 2015 4:35 PM (20 minutes)

The Transient High Energy Sky and Early Universe Surveyor (THESEUS) is a mission conceptdeveloped by a large international collaboration aimed at exploiting Gamma-Ray Bursts for inves-tigating the early Universe. The main scientific objectives of THESEUS include: investigating thestar formation rate and metallicity evolution of the ISM and IGM up to redshift 10, detecting thefirst generation (pop III) of stars, studying the sources and physics of re-ionization, detecting thefaint end of galaxies luminosity function. These goals will be achieved through a unique combina-tion of instruments allowing GRB detection and arcmin localizaiton over a broad FOV (more than1sr) and an energy band extending from several MeVs down to 0.3 keV with unprecedented sen-sitivity, as well as on-board prompt (few minutes) follow-up with a 0.6m class IR telescope withboth imaging and spectroscopic capabilities. Such instrumentation will also allow THESEUS tounveil and study the population of soft and sub-energetic GRBs, and, more in geeneral, performmonitoring and survey of the X_ray sky with unprecedented sensitivity.

Collaboration

THESEUS collaboration

Primary author: AMATI, Lorenzo (INAF - IASF Bologna)

Presenter: AMATI, Lorenzo (INAF - IASF Bologna)



28th Texas Symp … / Report of Contributions Measuring cosmological paramete …


Measuring cosmological parameters with GRBs:status and perspectives


Given their huge isotropic-equivalent radiated energies, up to more than 1054 erg released in a fewtens of seconds,and their redshift distribution extending up to more than z = 9, Gamma-Ray Bursts (GRB) are inprinciple a powerful tool formeasuring the geometry and expansion rate of the Universe. In the recent years, several attemptshave been made toexploit the correlation between the photon energy at which the νFν spectrum peaks (”peak en-ergy”) and the radiated energy (orluminosity) for “standardizing” GRBs and use them as tools (complementary to other probes likeSN Ia, BAO and the CMB) for the estimate of cosmologicalparameters. These studies show that already with the present data set GRBs can provide a signifi-cant and independentconfirmation of ΩM ∼ 0.3 for a flat ΛCDM universe and that the measurements expected frompresent and next GRBexperiments (e.g. Swift, Fermi/GBM, SVOM, CALET/GBM, UFFO) will allow us to substantiallyimprove the constraints on ΩM and ΩΛ, and, in particular, to get unique clues on dark energyproperties and evolution.

Primary author: AMATI, Lorenzo (INAF - IASF Bologna)

Presenter: AMATI, Lorenzo (INAF - IASF Bologna)



28th Texas Symp … / Report of Contributions Frame dragging, unipolar inductio …


Frame dragging, unipolar induction and Kerr blackhole magnetospheres


Making use of 3+1 formulation of black hole electrodynamics, it is argued that the frame-draggingeffect combines with unipolar induction, to sustain the double-structured magnetosphere consist-ing of the outer and inner domains, and high-energy activities therein. The emf’s,calEout andcalEin, of a pair of unipolar induction batteries driving electric currents in the two domains areequivalent to those due to a pair of magnetized rotators spinning anti-parallelly each other withΩF and −(ΩH−ΩF), located back-to-back at both sides of the interface SN at ω = ΩF in-between,where ΩF, ΩH and ω are the angular velocities of field lines, the Kerr hole and the frame draggingdue to the hole’s spin. The difference,calEout −calEin= ∆V = −(ΩH/2πc)∆Ψ, corresponding to the difference of the two angular velocities ofhypothetical rotators at SN, ΩF − [−(ΩH −ΩF]) = ΩH, will provide a voltage drop strong enoughto develop a magnetized gap in which pair-creation discharges will take place to provide copiouscharged particles to out- and in-flows in both domains and allow field lines pinned down to fixΩF with the local frame-dragging angular velocity, i.e., ΩF = ωN. Such a situation will allow oneto present the hole’s double structure in terms of a twin-pulsar model, consisting of a pulsar-typewind flowing toward infinity and an anti-pulsar-type wind flowing in toward the horizon, withthe common particle/current sources where field lines are pinned down(see I. Okamoto, PASJ, 2015, 67, 69)

Primary author: Prof. OKAMOTO, Isao (National Astronomical Observatory of Japan)

Presenter: Prof. OKAMOTO, Isao (National Astronomical Observatory of Japan)



28th Texas Symp … / Report of Contributions Exact solutions in astrophysics


Exact solutions in astrophysicsFriday, December 18, 2015 9:35 AM (35 minutes)

There are over 1300 known exact solutions to Einstein’s equations. Part of these solutions foundapplications in astrophysics including the solar system, compact objects, and cosmology. Thesehave offered some physical or mathematical insights into the systems under consideration. In thisreview talk, some characterizing notions about exact solutions will be outlined along with someexamples. After a brief presentation of some neutron star models, the discussion will focus oninhomogeneous cosmological models and their applications. The related problem of averaging inrelativity and cosmology will also be outlined.

Primary author: Prof. ISHAK, Mustapha (The University of Texas at Dallas)

Presenter: Prof. ISHAK, Mustapha (The University of Texas at Dallas)



28th Texas Symp … / Report of Contributions Lorentz violation in gravity


Lorentz violation in gravityTuesday, December 15, 2015 5:45 PM (25 minutes)

After briefly explaining why Lorentz violating theories of gravity are interesting for quantum grav-ity, I will discuss how they can be tested with current astrophysical and cosmological observations.

Primary author: BLAS TEMINO, Diego (CERN)

Presenter: BLAS TEMINO, Diego (CERN)



28th Texas Symp … / Report of Contributions Rattle and shine by compact binari …


Rattle and shine by compact binaries mergersWednesday, December 16, 2015 9:35 AM (35 minutes)

Compact binary systems are copious producers of gravitational waves andare also expected to radiate strongly electromagnetically. This talk willdescribe several processes –intrinsically requiring the strongly gravitating/highlydynamical behaviour of the system– that can yield observable signals in a varietyof frequencies. Moreover, we will discuss how such radiation might provefundamental in answering key questions about their components and gravity itself.

Primary author: Prof. LEHNER, Luis (Perimeter Institute)

Presenter: Prof. LEHNER, Luis (Perimeter Institute)



28th Texas Symp … / Report of Contributions Search of the primordial gravitatio …


Search of the primordial gravitational waves withVery Long Baseline Interferometry


Some models of the expanding Universe predict that the astrometric proper motion of distant radiosources embedded in space-time are non-zero as radial distance from observer to the source grows.Systematic proper motion effects would produce a predictable quadrupole pattern on the sky thatcould be detected using Very Long Baseline Interferometry (VLBI) technique. This quadrupolepattern can be interpreted either as an anisotropic Hubble expansion, or as an indication of theprimordial gravitational waves in the early Universe.

We have analyzed a large set of geodetic VLBI data spanning from 1979 till 2015 toestimate the quadrupole harmonics in the expansion of the vector field of the proper motions ofquasars in the sky. We estimated the vector spherical harmonics (three parameters for the dipoleand ten - for the quadrupole systematic) by means of analysis of the intermediate individual propermotion. Additionally, the same estimates have been obtained separately for different red shiftzones. The results of analysis are presented in this paper.

Primary author: Dr TITOV, Oleg (Geoscience Australia)

Co-author: Dr LAMBERT, Sebastien (Paris Observatory)

Presenter: Dr TITOV, Oleg (Geoscience Australia)



28th Texas Symp … / Report of Contributions How to use geodetic VLBI to meas …


How to use geodetic VLBI to measure relativisticlight deflection from extragalactic objects


The Sun’s gravitational field deflects the apparent positions of close objects in accordance with theformulae of general relativity. Optical astrometry is used to test the prediction, but only with thestars close to the Sun and only during total Solar eclipses. Nowadays, more advanced technique,geodetic Very Long Baseline Interferometry (VLBI) is applied for testing of general relativity withprecision about 0.01 percent. The geodetic VLBI is capable of measuring the gravitational delaybased on the differential Shapiro’s delay. By reason, the gravitational delay is equivalent to thedeflection of the light from distant radio sources and could be measured at anytime and across thewhole sky. In accordance with the theory, all celestial objects display annual circular motion withthe magnitude proportional to their ecliptic latitude due to the Earth orbital motion. In particular,the objects near the ecliptic pole draw an annual circle with magnitude of 4 millisecond of arc.

In contrast to the optical facilities, a single ground-based VLBI interferometer is made of two radiotelescopes separated by several thousand kilometers. This provides an additional advantage todetect a secondary light deflection angle caused by the parallactic shift of the Sun as observedfrom both ends of the interferometer. This effect is proportional to the baseline length and is about0”.01 for grazing light at baseline of 8000 km. It could be used in future space interplanetary VLBImissions with baseline length of one billion kilometers (comparable to the Jupiter orbit size) fordirect detection of invisible mass from extragalactic objects.

Primary author: TITOV, Oleg

Co-author: Mrs GIRDIUK, Anastasiia (Technical University of Vienna)

Presenter: TITOV, Oleg



28th Texas Symp … / Report of Contributions Exploring the Ultra High Energy C …


Exploring the Ultra High Energy Cosmic Rays withthe Pierre Auger Observatory


The Pierre Auger Observatory studies the most energetic cosmic rays arriving at Earth, in theenergy range from 10^17 eV up to 10^20 eV and beyond. More than 10 years data taking haveled to major advances in our knowledge of the origin and nature of cosmic rays. We present asummary of the latest results, discussing the challenges on the astrophysical interpretation of theflux suppression observed above 4 10^19 eV imposed by the experimental results on the primarycosmic ray composition and anisotropy.

Collaboration

The Pierre Auger Collaboration

Primary author: PETRERA, Sergio (University of L’Aquila)

Presenter: PETRERA, Sergio (University of L’Aquila)



28th Texas Symp … / Report of Contributions Multiwavelength Spectral and Pol …


Multiwavelength Spectral and PolarizationSignatures of Shocks in Relativistic Jets


This talk reviews recent progress in our understanding of the multiwavelength spectral and polar-ization signatures of relativistic shocks in the relativistic jets of active galactic nuclei and gamma-ray bursts. Spectral signatures are based on a self-consistent coupling of Monte-Carlo simulationsof diffusive shock acceleration with radiation-transfer simulations. Our results indicate that, inorder to reproduce the spectral energy distributions of blazars, the pitch-angle scattering meanfree path of electrons has to be strongly energy dependent. Polarization signatures of relativisticshocks are based on polarization-dependent radiation transfer simulations, indicating that largepolarization-angle rotations result naturally in a straight jet pervaded by a helical magnetic field.Simultaneous fits to the SEDs, multiwavelength light curves, and time-dependent synchrotron po-larization signatures from the prominent polarization-angle swing event in 3C279 are presented.

Primary author: BOETTCHER, Markus (North-West University)

Co-authors: Dr SUMMERLIN, Errol (Goddard Space Flight Center); Mr ZHANG, Haocheng (LosAlamos National Lab); Prof. BARING, Matthew (Rice University)

Presenter: BOETTCHER, Markus (North-West University)



28th Texas Symp … / Report of Contributions First hundred years of GR: success …


First hundred years of GR: successes, status andprospects

Monday, December 14, 2015 9:35 AM (35 minutes)

General Relativity revolutionized the way we we thought about gravity. After describing brieflythe key successes of GR and their impact, I will discuss the major conceptual challenges it facestoday. I will conclude by outlining the prospective future directions of development, which holdthe promise for deepening our understanding of the nature of gravity further.

Primary author: Prof. PADMANABHAN, Thanu (ICAA Pune)

Presenter: Prof. PADMANABHAN, Thanu (ICAA Pune)



28th Texas Symp … / Report of Contributions The H.E.S.S. Extragalactic Sky


The H.E.S.S. Extragalactic SkyWednesday, December 16, 2015 2:00 PM (25 minutes)

The High Energy Stereoscopic System H.E.S.S. is an array of 5 Imaging Atmospheric CherenkovTelescopes located in the Khomas Highland, Namibia. The first four 12m-diameter telescopes areoperating since 2003 and a fifth telescope (a 28m diameter dish) had been added to the array in 2012improving the sensitivity of the array towards lower energies. In this talk, I will present highlightof recent results of H.E.S.S. on AGN observations such as blazars (PKS 2155-304, Mrk 501, PG1553+113, 1ES 0229+200) but also non-blazars AGNs (e.g radio-galaxies), extragalactic backgroundlight (EBL) and an update on the H.E.S.S. Gamma-Ray Burst program.

Collaboration

H.E.S.S.

Primary author: CHEVALIER, Jill (LAPP)

Presenter: CHEVALIER, Jill (LAPP)



28th Texas Symp … / Report of Contributions Multi-wavelength variability of th …


Multi-wavelength variability of the gamma-raybinary LS I +61 303 along the super-orbital period


Detected from radio to TeV gamma rays, the gamma-ray binary LS I + 61º303 is highly variableacross all frequencies. Beside its variability due to the modulation of its emission due to the 26.496-day orbital period, the system also presents variability consistent with the so-called superorbitalperiod, of 1667 days. We will present the latest data set of LSI +61º 303 taken with the FermiLarge Area Telescope and put it in a multi-wavelength context. Furthermore, we show for the firsttime that not only at GeV energies but also in other bands, the superorbital modulation is moreprominently seen at orbital phases around apastron, whereas it does not introduce a visible changeclose to periastron. Finally, we present correlation studies between GeV, X-ray, optical, and radiodata and comment on a physical, pulsar-based scenario which could explain the behavior of thisenigmatic binary.

Primary author: Prof. TORRES, Diego (ICREA / Institute of Space Sciences)

Co-author: Dr HADASCH, Daniela (ICRR, Tokyo)

Presenter: Prof. TORRES, Diego (ICREA / Institute of Space Sciences)



28th Texas Symp … / Report of Contributions The quest for a stochastic backgro …


The quest for a stochastic background withLIGO/VIrgo GW detectors


According to various cosmological scenarios, we are bathed in a stochastic background of gravita-tional waves generated in the first instants after the Big Bang. Detection of this background wouldhave a profound impact on our understanding of the evolution of the Universe, as it represents aunique window on the very early Universe and on the physical laws that apply at the highest en-ergy scales.In addition to the cosmological background, an astrophysical background may have resulted fromthe superposition of a large number of unresolved sources since the beginning of stellar activity.This astrophysical contribution could be a foreground masking the cosmological background butit can also provide very interesting informations, not only about the physical properties of the re-spective astrophysical populations, complementing individual GW detections, but also about theevolution of these objects with redshift, the star formation history or the metallicity.In this talk, I will give an overview of the different sources and present the data analysis methodsused in the LIGO/Virgo collaboration to measure the energy density of the GW background. I willdiscuss the first 3-months observational run of Advanced LIGO (fall 2015) as well as the accessi-bility of the different models and the constrains we expect to put on their parameters in the nextfew years and with third generation detectors like Einstein Telescope.

Primary author: REGIMBAU, Tania (Observatoire de la Côte d’Azur)

Presenter: REGIMBAU, Tania (Observatoire de la Côte d’Azur)



28th Texas Symp … / Report of Contributions Relativistic line reverberation map …


Relativistic line reverberation mapping in tidaldisruption events


When normal stars run close enough to the previously dormant supermassive black holes (SMBHs)at the centres of normal galaxies, they would be entirely or partly disrupted due to the tidal force,leading to the so-called tidal disruption events (TDEs). Part of the debris material will be accretedby the SMBHs later on. The accretion of the debris material would generate X-ray flares, which willilluminate the remaining debris material and would generate spectral line feature in their spectra.Here we show predicted features due to relativistic spectral lines expected to occur during theaccretion phase of the debris material. We demonstrate that these spectral features can be used toprobe the mass and spin of the SMBHs at the centres of galaxies as well as the accretion geometryand GR effects involved in the TDE events.

Primary author: YU, Wenfei (Shanghai Astronomical Observatory)

Co-authors: Dr DOVCIAK, Michal (Astronomical Institute, Czech Academy of Sciences); Prof.KARAS, Vladimir (Astronomical Institute, Czech Academy of Sciences); Dr ZHANG, Wenda (ShanghaiAstronomical Observatory)

Presenter: YU, Wenfei (Shanghai Astronomical Observatory)



28th Texas Symp … / Report of Contributions Multi-scale modelling of pulsar gli …


Multi-scale modelling of pulsar glitchesTuesday, December 15, 2015 2:21 PM (21 minutes)

Neutron stars are an exceptional fundamental physics laboratory, and provide us with the onlyopportunity to study the strong interaction at high densities and low temperatures. These objectsare, in fact, not only very dense (with central densities surpassing nuclear saturation density),but also cold, as their thermal energy is generally negligible compared to the Fermi energy of theconstituents. This will modify the dynamics of the system considerably, with large scale superfluidsexpected in the interior.Observations of radio pulsar glitches offer what is considered to be a probe of the dynamics ofthe superfluid in NS interiors. Glitches, i.e. sudden jumps in the spin frequency of the pulsar, aregenerally thought to be due to a large scale superfluid component that is decoupled from the spin-down of the ‘normal’ component, and then recouples catastrophically, giving rise to the observedsignal. This is a fascinating macroscopic effect of small scale, quantum, properties of a superfluid.A superfluid rotates by forming an array of quantised vortices, which can ‘pin’ to ions in the crustor flux-tubes in the core, preventing the superfluid neutron component from expelling vorticityand spinning down with the rest of the star.Previous work has been successful in separately modelling vortex motion on microscopic scalesand the large scale hydrodynamics of the star.In this talk I will present recent work that aims to bridge this gap in scales and consistently modelthe whole glitch process. I will discuss analytical and numerical work to extend the results ofsmall scale quantum mechanical simulations to larger scales, and how these results can be used inhydrodynamical simulations, possibly to explain the recently observed size distribution of glitchesin the Crab pulsar.

Primary author: HASKELL, Brynmor (The University of Melbourne)

Presenter: HASKELL, Brynmor (The University of Melbourne)



28th Texas Symp … / Report of Contributions The ultraluminous pulsar


The ultraluminous pulsarTuesday, December 15, 2015 2:00 PM (25 minutes)

M82 X-2, an ultraluminous X-ray source in M82, was recently shown to harbor an accreting neu-tron star. Its luminosity being ~100 times the Eddington limit for a neutron star, it poses someproblems to the existing theoretical framework about accretion onto neutron stars.I will talk about the proprieties and behavior of this source, how it was unveiled as a neutron star,the possible theoretical interpretations and some preliminary results coming from new observa-tions of the M82 field.

Primary author: BACHETTI, Matteo (INAF/Osservatorio Astronomico di Cagliari)

Presenter: BACHETTI, Matteo (INAF/Osservatorio Astronomico di Cagliari)



28th Texas Symp … / Report of Contributions The Cherenkov Telescope Array


The Cherenkov Telescope ArrayThursday, December 17, 2015 2:00 PM (24 minutes)

As an observatory for ground-based gamma-ray astronomy in the energy region from a few tensof GeV to a few hundred TeV, the Cherenkov Telescope Array (CTA) will be the major next gener-ation facility of Imaging Atmospheric Cherenkov Telescopes. The broad energy coverage will beaccompanied by an order of magnitude improvement in flux sensitivity in the TeV region alongwith factor 2-5 improvements in angular and energy resolution compared to the current gener-ation of instruments. These improvements in performance will come from the use of multipledesigns of wide field-of-view telescope, each optimised for a particular energy region, arranged inextensive arrays. Full sky coverage will come from having arrays at two sites, one in the southernhemisphere and another in the northern. CTA will operate as an open access observatory to theastrophysics community and run a Key Science Programme to provide legacy datasets and addresstopics of both high-energy astrophysics and fundamental physics. This talk will review the statusof the CTA project as it enters its pre-construction phase.

Collaboration

the CTA consortium

Primary author: DANIEL, Michael (University of Liverpool)

Presenter: DANIEL, Michael (University of Liverpool)



28th Texas Symp … / Report of Contributions Dynamics of compact binaries at t …


Dynamics of compact binaries at the fourthpost-Newtonian approximation


Coalescing compact binary systems are among the most promising sources of gravitational wavesfor the next generations of interferometers. Due to the faintness of the signal, one needs to con-struct highly accurate templates to be match-filtered against the detector data, for both detectionand parameter estimation. During the inspiralling phase of the coalescence, when the two objectsare widely separated, the post-Newtonian (PN) formalism allows one to describe the dynamics ofthe binary and to compute the radiation energy flux, from which the orbital phase evolution canbe derived. In this talk, I will present the equations of motion of non-spinnning compact binarysystems derived at 4PN in harmonic coordinates. In particular I will detail the formalism based ona Fokker action, including the treatment of the so-called tail effects which appear at 4PN.

Primary author: Ms BERNARD, Laura (IAP)

Presenter: Ms BERNARD, Laura (IAP)



28th Texas Symp … / Report of Contributions Rapid particle acceleration at perp …


Rapid particle acceleration at perpendicular shocksMonday, December 14, 2015 5:35 PM (20 minutes)

Perpendicular shocks are shown to be rapid astrophysical particleaccelerators. They perform optimally when the ratio ofthe shock speed to the particle speed roughly equals the ratioof the scattering rate to the gyro frequency. Analytical methodsand Monte-Carlo simulations are used to solve thekinetic equation that govern the anisotropy generated at theseshocks, finding a softer spectralindex than the standard result of diffusive shock acceleration, and anacceleration time significantly shorter than the frequently quoted “Bohm limit”.Amongst other implications, these results provide a theoretical basis forthe thirty-year-old conjecture that a supernova exploding into thewind of a Wolf-Rayet star may accelerate protons to an energyexceeding 1015 eV.

Primary author: KIRK, John

Co-author: Dr TAKAMOTO, Makoto (Department of Earth and Planetary Science, The Universityof Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan)

Presenter: KIRK, John



28th Texas Symp … / Report of Contributions Missing hard states and regular ou …


Missing hard states and regular outbursts: thepuzzling case of the BHC 4U 1630–472


4U 1630–472 is a recurrent X-ray transient classified as a black hole candidate from its spectral andtiming properties. One of the peculiarities of this source is the presence of regular outburstswith a recurrence period between 600 and 730 d that has been observed since the discovery of thesource in 1969. We report on a comparative study, performed with INTEGRAL and RXTE, of thespectral and timing behaviour of four consecutive outbursts that occurred in 2006, 2008, 2010 and2012.We show that, in spite of having a very similar accretion disc evolution, these four outbursts ex-hibit totally different characteristics of the Compton electron corona, showing a softening in theirevolution rarely observed before in a low-mass X-ray binary hosting a black hole.We argue the possibility that the unknown perturbation that causes the outbursts to be equallyspaced in time could be at the origin of this particular behaviour. We describe several possiblescenarios that could explain the regularity of the outbursts, identifying the most plausible, such asa third body orbiting around the binary system.

Collaboration

Capitanio F., Campana R., De Cesare G., Ferrigno C.

Primary author: Dr CAPITANIO, Fiamma (IAPS-INAF)

Presenter: Dr CAPITANIO, Fiamma (IAPS-INAF)



28th Texas Symp … / Report of Contributions Lense-Thirring precession in stron …


Lense-Thirring precession in strong gravitationalfieldsMonday, December 14, 2015 3:03 PM (21 minutes)

The exact Lense-Thirring precession frequencies for Kerr, Kerr–Taub–NUT,Taub–NUT, Plebanski-Demianski spacetimes are explicitly derived. Remarkably, in the case of the zero angular momen-tum Taub–NUT spacetime, the frame-dragging effect is shown not to vanish, when consideredfor spinning test gyroscopes. In the case of the interior of the rotating neutron stars, the exactframe-dragging rate monotonically decreases from the center to the surface along the pole andalong the equatorial distance, it decreases initially away from the center, becomes negligibly smallwell before the surface of the neutron star, rises again, and finally approaches to a small value atthe surface. The appearance of a local maximum and minimum in this case is the result of thedependence of frame-dragging frequency on the distance and angle. Moving from the equator tothe pole, it is observed that this local maximum and minimum in the frame-dragging rate alongthe equator disappear after crossing a critical angle. It is also noted that the positions of the lo-cal maximum and minimum of the frame-dragging rate along the equator depend on the rotationfrequency and central energy density of a particular pulsar. The same anomaly can also be foundin the case of Kerr–Taub–NUT spacetime but it is along the pole. Presently, direct observation ofthe Lense-Thirring precession of a classical or quantum spin vector relative to local inertial framesdragged along a timelike curve in any stationary spacetime is impossiblein the presence of strong gravitational fields. Analogue models of black holes offer an alternativeoption of its indirect measurement in a comparatively accessible laboratory setup. We deduce pre-cise estimate of the angular velocity of precession of a test spin outside the ergoregion of a fluidmechanical rotating “dumb hole” in acoustic spacetimes. It is our hope that with present technolog-ical expertise in manipulating analogue black holes, experimentalists will be able to successfullyverify our estimate and hence, more importantly, the predicted strong gravity Lense-Thirring effect.

Primary author: Dr CHAKRABORTY, Chandrachur (Tata Institute of Fundamental Research , Mum-bai , INDIA)

Presenter: Dr CHAKRABORTY, Chandrachur (Tata Institute of Fundamental Research , Mumbai ,INDIA)



28th Texas Symp … / Report of Contributions Gravitational lensing flexion meas …


Gravitational lensing flexion measurements in theHubble Frontier Fields


Flexion is the second order weak gravitational lensing effect which is responsible for the arclikeappearance of lensed sources. Its strong signal in the intermediate regime and the orthogonalityto the weak lensing shear field make flexion an ideal complement to today’s gravitational lensingmeasurements. Furthermore, its high sensitivity to local density peaks makes it a great tool fordetecting substructure and thus for constraining the halo mass function. This could potentially dis-tinguish cold and warm dark matter scenarios. However, flexion measurements have proved to bedifficult up to now. The high quality of the Hubble Frontier Fields, a major observing program withthe Hubble Space Telescope to provide unprecedented deep observations of 6 strong lensing clusters,makes this data set a prime target for flexion measurements. We present an automated measure-ment pipeline and substructure constraints from its application to the clusters MACSJ0416.1-2403and Abell 2744.

Primary author: Mr REXROTH, Markus (EPFL - EPF Lausanne)

Co-author: Prof. KNEIB, Jean-Paul (EPFL)

Presenter: Mr REXROTH, Markus (EPFL - EPF Lausanne)



28th Texas Symp … / Report of Contributions Critical Collapse of Radiation Flui …


Critical Collapse of Radiation Fluids: Deviationsfrom Spherical Symmetry


We study critical phenomena in the gravitational collapse of a radiation fluid. We perform numer-ical simulations in both spherical symmetry and axisymmetry, and observe critical scaling in bothsupercritical evolutions, which lead to the formation of a black hole, and subcritical evolutions,in which case the fluid disperses to infinity and leaves behind flat space. We identify the criticalsolution in spherically symmetric collapse, and study the approach to this critical solution in theabsence of spherical symmetry. Our simulations are performed with an unconstrained evolutioncode, implemented in spherical polar coordinates, and adopting “moving-puncture” coordinates.

Primary author: BAUMGARTE, Thomas (Bowdoin College)

Presenter: BAUMGARTE, Thomas (Bowdoin College)



28th Texas Symp … / Report of Contributions Measuring the Innermost Stable C …


Measuring the Innermost Stable Circular Orbits ofSupermassive Black Holes


We present a promising new technique (g-distribution method) for measuring the innermost sta-ble circular orbit (ISCO), the inclination angle (i), and the spin of a supermassive black hole. Theg-distribution method involves measurements of the distribution of the energy shifts of the rela-tivistic iron line emitted from the accretion disk of a supermassive black hole that is microlensedby stars in a foreground galaxy and a comparison of the measured g-distribution with microlens-ing caustic simulations. The method has been applied to the gravitationally lensed quasar RXJ1131−1231 and initial results indicate that r_ISCO < 9 gravitational radii and i < 60 degrees. Fur-ther monitoring of RX J1131−1231 and other lensed quasars will provide tighter constraints on theinclination angles, ISCO radii and spins of the black holes of distant quasars.

Primary author: Dr CHARTAS, George (College of Charleston)

Co-author: Mr RHEA, Carter (College of Charleston)

Presenter: Dr CHARTAS, George (College of Charleston)

28th Texas Symp … / Report of Contributions Simulating the effect of massive n …


Simulating the effect of massive neutrinos onlarge-scale structure


The massive neutrino background makes up a component of the dark matter, and as such affectsthe growth of large-scale structure, such as galaxy clusters. This affords us an opportunity to mea-sure the neutrino mass. However, to do this we must accurately and efficiently characterize howneutrinos affect structure growth. I will describe a new method for including massive neutrinos inN-body simulations which is uniquely accurate in the limit of small neutrino masses, and incurs nocost above that of the N-body simulation. It uses perturbation theory for the neutrinos, modifiedto include source terms for the non-linear dark matter clustering. A small fraction of low-energyneutrinos which cluster more strongly may be treated as particles, but this does not substantiallyaffect the overall structure.

Primary author: Dr BIRD, Simeon (Johns Hopkins University)

Presenter: Dr BIRD, Simeon (Johns Hopkins University)



28th Texas Symp … / Report of Contributions Exotic Rotational Correlations in E …


Exotic Rotational Correlations in EmergentQuantum Geometry


It is proposed that small amplitude, coherent rotational fluctuations arise from the emergence ofnearly-classical non-rotating inertial frames from Planck scale quantum elements. An exact formis calculated for Planck scale correlations in the signal of a Sagnac type interferometer, where thelight path encloses a large area of arbitrary shape, normalized using area quantization from LoopQuantum Gravity.It is conjectured that such Planck scale rotational fluctuations, entangled with the strong interac-tion vacuum, may determine the value of the cosmological constant. Cosmic acceleration may beviewed as centrifugal acceleration by rotational fluctuations of the matter vacuum.An experiment concept is sketched, based on a reconfiguration of the Fermilab Holometer.

Primary author: HOGAN, Craig (U. Chicago and Fermilab)

Presenter: HOGAN, Craig (U. Chicago and Fermilab)

Session Classification: 06 - Early universe


28th Texas Symp … / Report of Contributions The long-term optical study of VH …


The long-term optical study of VHE blazarsTuesday, December 15, 2015 6:35 PM (3 minutes)

To study optical variability of extragalactic objects, namely VHE blazars, we are conducting inAbastumani Observatory since 1997 a long-term campaign using dedicated telescopes, which al-lowed to collect ~300 000 CCD frames during 2 800 nights. This extensive monitoring campaignover 100 blazars during five years was carried out in BVRI bands and later on from 2002 mainlyin R band using the 70-cm meniscus (f/3, SBIG ST6 and Apogee Ap6E), 125-cm Ritchey-Chretien(f/13, Apogee Ap6E) and Calar-Alto Observatory (123-cm and 220-cm) telescopes. Most denselysampled sources are 1ES 0229+200, 1ES 0806+524, 1ES 1011+496, Mrk 421 Mrk 501, 1ES 1221+302,Pg 1553+113, 1ES 1959+650, 1ES 2344+514 and others.The frames have been reduced using Daophot II and homogenous sample of lightcurves have beenconstructed. The amplitudes of long-term variability are within 0.3-1.5 magnitudes. Few sourcesshow Intra-day variability within 0.05-0.15 magnitudes, while intra-night/micro-variability is be-low 0.05 magnitudes. The results of multiwavelength campaigns with Whipple, VERITAS, HESSand MAGIC are also presented. To extend in the future optical photometric, polarimetric and spec-tral survey of fainter sources with high temporal resolution, we are considering purchase of twoPanSTAR like telescopes.

Primary author: KURTANIDZE, Omar (Abastumani Observatory)

Presenter: KURTANIDZE, Omar (Abastumani Observatory)



28th Texas Symp … / Report of Contributions Cosmology with the Dark Energy …


Cosmology with the Dark Energy SurveyThursday, December 17, 2015 3:24 PM (21 minutes)

The Dark Energy Survey (DES) is a 5000 square degree survey targeting dark matter and darkenergy science. This year sees the release of the first science results from the DES collaborationusing data taken during science verification. I plan to present these new results, which includedark matter maps, cosmology constraints and new discoveries such as the new strong lens systemsbeing found. I will also give an update on the progress of the main science survey.

Primary author: Dr AMARA, Adam (ETHZ - ETH Zurich)

Presenter: Dr AMARA, Adam (ETHZ - ETH Zurich)



28th Texas Symp … / Report of Contributions Imaging a boson star at Sgr A*


Imaging a boson star at Sgr A*Thursday, December 17, 2015 4:55 PM (20 minutes)

Near-future sub-millimetric VLBI observations of the surroundings of the Galactic center super-massive black hole, Sgr A, by the Event Horizon Telescope (EHT) will lead to unprecedented con-straints on the nature of the accretion flow surrounding this compact object. One of the most fascinat-ing goal of the EHT is to test the presence of an event horizon by imaging theblack hole shadow, andto constrain the Kerr metric by measuring the so-calledphoton ring*.

The goal of my talk will be to present the first simulations of an accretion flow at Sgr Aassumingthat this compact object is no longer a black hole, but a boson star. Such an object is a long-studiedalternative to black holes, which does not possess any event horizon, nor any singularity. I will showimages and spectra of an accretion torus surrounding a boson star at Sgr A, and discuss the specificobservational properties of rotating boson stars as opposed to Kerr black holes. I will focus inparticular on the (im)possibility to demonstrate the existence of an event horizon from detectingSgr A* shadow.

Collaboration

F. H. Vincent, Z. Meliani, P. Grandclément, E. Gourgoulhon, O. Straub

Primary author: Dr VINCENT, Frederic (Observatoire de Paris)

Presenter: Dr VINCENT, Frederic (Observatoire de Paris)



28th Texas Symp … / Report of Contributions Vela X-1 and sgHMXB: hydro driv …


Vela X-1 and sgHMXB: hydro driven hard X-raysMonday, December 14, 2015 5:05 PM (20 minutes)

The dynamic of the accretion of stellar wind on the pulsar in Vela X-1 is dominated by unsta-ble hydrodynamical flows. INTEGRAL discovered off-states, 1037 erg/s flares, quasi-periodic oscillations and log normal flux distribution, which can all be reproduced by hydrodynam-ical simulations, revealing the complex motion of the bow shocks moving either towards or awayfrom the neutron star. With the help of hydrodynamic simulations and hard X-ray observationscan also be used to probe the scattering of hard X-ray photons on the stellar wind to determinethe velocity and density profile of the wind very close to the surface of the supergiant companion.This provides a unique measurement of the early acceleration of stellar winds in massive stars,otherwise poorly constrained.

Primary author: MANOUSAKIS, Antonis


Presenter: MANOUSAKIS, Antonis

28th Texas Symp … / Report of Contributions Quasi-periodic oscillations from re …


Quasi-periodic oscillations from relativistichydrodynamical slender tori


We simulate a purely hydrodynamical torus with constant specific angular momentum arounda Schwarzschild black hole. The goal is to search for quasi-periodic oscillations (QPOs) of thetorus. Initial torus setup is subjected to radial, vertical and a diagonal (combination of radial andvertical) velocity perturbations. The hydrodynamical simulations are performed using the gen-eral relativistic magnetohydrodynamics code Cosmos++ and ray-traced using the GYOTO code.We found that exciting radial perturbations also trigger a plus mode, while vertical perturbationstrigger an X-mode. The diagonal perturbation gives just a combination of radial and vertical per-turbation. Existing radially perturbed hydrodynamic simulations are in full agreement with ourfindings. The behavior of QPOs in slender torus mimics those of non-slender torus. This confirmsthat in actual astrophysical accretion disks, no matter the model (thin, slim, thick), the QPOs willalways be detected.

Primary author: MISHRA, Bhupendra (Nicolaus Copernicus Astronomical Center Warsaw Poland)

Co-authors: MANOUSAKIS, Antonis; VINCENT, Frederic (Observatoire de Paris)

Presenters: MANOUSAKIS, Antonis; MISHRA, Bhupendra (Nicolaus Copernicus AstronomicalCenter Warsaw Poland); VINCENT, Frederic (Observatoire de Paris)



28th Texas Symp … / Report of Contributions Joint Constraints on Neutrino Mas …


Joint Constraints on Neutrino Masses fromCosmology and Particle Physics


The absolute scale of neutrino masses is one of the main open issues both in cosmology and particlephysics. Current experimental strategies involve i) measurements exploiting kinematics effects inbeta decay, ii) searches for neutrinoless double beta decay (’0n2b’), and iii) cosmological observa-tions. The three approaches are complementary, each of them presenting its own advantages anddisadvantages, and also because they are sensitive to slightly different quantities related to the neu-trino masses. In this work, we want to derive joint constraints on neutrino mass parameters fromthe most recent observations from both laboratory and cosmological experiments, and forecasts,combining them in the framework of Bayesian statistics. In particular, for ‘0n2b’ experiments, wetake into account the uncertainty related to nuclear matrix elements, in order to account its impacton the neutrino mass estimates.

Primary author: GERBINO, Martina (University of Rome ’Sapienza’)

Co-authors: MELCHIORRI, Alessandro; Dr LATTANZI, Massimiliano (Università di Ferrara andINFN)

Presenter: GERBINO, Martina (University of Rome ’Sapienza’)



28th Texas Symp … / Report of Contributions A model for distortions of polarisa …


A model for distortions of polarisation angle in radiopulsars


Average profilesof some radio pulsars containweak emission components which cover large intervals of pulse phaseas well as localised emission or absorption features.The polarisation-angle (PA) under such features exhibitslocal distortions which cannot be explained through the rotating vector modeland other effects such as the special relativistic effects ormodification of magnetic fields.We show that some of these distortions in the average PA curvecan be explained using a simplified physical modelof an extended microbeam of the X-mode curvature radiation.Successful interpretation will be presentedfor features with very different polarisation characteristics, such as thebifurcated emission component on the trailing side of the profile ofJ0437-4715, and for the double notches observed in B1821-24A and J0437-4715.

Primary author: SAHA, Lab (Nicolaus Copernicus Astronomical Center, Torun, Poland)

Co-authors: Prof. RUDAK, Bronislaw (Nicolaus Copernicus Astronomical Center, Torun, Poland); DrCOGNARD, Ismael (LPC2E / OSUC, France); Dr JAROSLAW DYKS, Jaroslaw (Nicolaus Copernicus As-tronomical Center, Torun, Poland); Dr GUILLEMOT, Lucas (LPC2E / OSUC, France); Dr SERYLAK,Maciej (Universtity of the Western Cape, Cape Town, South Africa); Dr OSLOWSKI, Stefan (Bielefeld,Germany)

Presenter: SAHA, Lab (Nicolaus Copernicus Astronomical Center, Torun, Poland)



28th Texas Symp … / Report of Contributions Award ceremony

Contribution ID: 133 Type: not specified

Award ceremonyThursday, December 17, 2015 11:40 AM (10 minutes)

Primary author: Prof. TRIMBLE, Virginia (University of California Irvine)

Presenter: Prof. TRIMBLE, Virginia (University of California Irvine)



28th Texas Symp … / Report of Contributions Resistive GRMHD simulations of a …


Resistive GRMHD simulations of accretion disksaround Kerr black holes: connecting large and small

scalesThursday, December 17, 2015 4:15 PM (21 minutes)

Accretion on compact objects is commonly considered the most plausible mechanism to power upa list of astrophysical systems (such as AGNs, GRBs, X-Ray Binaries, etc. . . ) and in particularmagnetic fields are believed to play a major role in enabling the accretion process through thedevelopment of magnetic instabilities. We investigated the effects of a finite resistivity in a mag-netized plasma orbiting around a rotating black hole in a fully covariant framework, providinga self-consistent closure for the Ohm law and performing 3D GRMHD simulations with a highlyparallelized version of the ECHO code.We studied in particular the development of the Papaloizou-Pringle instability (PPI) and how it isaffected by non-ideal effects, starting with different magnetic configurations and disk models.We also investigate the effects of a mean-field dynamo closure on axisymmetric disks, in order toaddress the question about the origin of the large-scale magnetic fields required in such systems:starting from a kinematic regime, we extend previous results to take into account a fully dynamicaldevelopment of the magnetic field through a quenched αΩ-dynamo.

Primary author: BUGLI, Matteo (Max Planck Institute for Astrophysics)

Co-authors: Dr MUELLER, Ewald (Max Planck Institute for Astrophysics); Dr DEL ZANNA, Luca(Universita’ degli Studi di Firenze); Dr BUCCIANTINI, Niccolo’ (INAF); Dr MONTERO, Pedro (MaxPlanck Institute for Astrophysics)

Presenter: BUGLI, Matteo (Max Planck Institute for Astrophysics)



28th Texas Symp … / Report of Contributions Swift and the Supergiant Fast X- …


Swift and the Supergiant Fast X-ray Transientoutburst factory


We present the results of the Swift Supergiant Fast X-ray Transients project,which has been exploiting Swift‘s capabilities in a systematic study of SFXTs and classicalsupergiant X-ray binaries (SGXBs) since 2007.The unique combination of sensitivity and scheduling flexibility of Swift/XRTallowed us to perform an efficient long-term monitoring of 16 including both SFXTs and classicalSGXBs.We followed source activity across more than 4 orders of magnitude in X-ray luminosity and sam-pled the light curves on timescales spanning from hours to years.Our measurements of dynamic ranges, duty cycles as a function of luminosity, and ofluminosity distributions show systematic differences thathelp discriminate between different models of SFXTs/SGXBs, while our outburst follow-upsprovide a steady advancement in the comprehension of the SFXT phenomenon.In particular, the observations of the SFXT prototype IGR J17544-2619on 2014 October 10, when the source reached a peak luminosity of 3× 1038 erg s−1,challenged, for the first time, the maximum theoretical luminosity achievableby a wind-fed neutron star high mass X-ray binary. We propose that this giant outburst was dueto the formation of atransient accretion disc around the compact object.

Primary author: ROMANO, Patrizia (INAF)

Co-authors: BURROWS, David (The Pennsylvania State University); BOZZO, Enrico (ISDC); KRIMM,Hans (NASA Goddard Space Flight Center); KENNEA, Jamie A. (The Pennsylvania State University); DUCCI,Lorenzo (University of Tuebingen); GEHRELS, Neil (NASA Goddard Space Flight Center); ESPOSITO,Paolo (National Institute for Astrophysics - INAF); EVANS, Phil (University of Leicester); BARTHELMY,Scott (NASA Goddard Space Flight Center); VERCELLONE, Stefano (INAF)

Presenter: ROMANO, Patrizia (INAF)



28th Texas Symp … / Report of Contributions Stability of relativistic two- …


Stability of relativistic two-component jetsWednesday, December 16, 2015 5:59 PM (20 minutes)

Several observations of astrophysical jets show evidence of a structure in the direction perpendic-ular to the jet axis, leading to the development of “spine & sheath” models of jets.

Two-component jets have been already examined (e.g. Meliani & Keppens 2007, Meliani & Keppens2009) for relativistic hydrodynamic jets and relativistic magnetized jets with poloidal magneticfield. These studies focused on a two-component jet consisting of a highly relativistic inner jetand a slower - but still relativistic - outer jet surrounded by an unmagnetized environment. Thesejets were susceptible to a relativistic Rayleigh-Taylor-type instability, depending on the effectiveinertia ratio of the two components.

This work is now extended by taking into account the presence of a non-zero toroidal magneticfield. We examine analytically the stability of this configuration and also perform numerical sim-ulations, using MPI-AMRVAC, to compare with the previously studied cases. Depending on theconfiguration, the toroidal magnetic field might stabilize the previously mentioned case or triggerinstabilities on a different time scale. Furthermore, the introduction of a toroidal magnetic fieldcomponent allows examining different types of relativistic jets (Poynting dominated or matterdominated) by modifying the magnetization parameter. Thus, we can investigate different combi-nations of matter/ Poynting dominated two-component that will end up (un)stable.

Collaboration

Rony Keppens & Zakaria Meliani

Primary author: Mr MILLAS, Dimitrios (KU LEUVEN)

Co-authors: Prof. KEPPENS, Rony (KU Leuven); Dr MELIANI, Zakaria (LUTH, Observatoire deParis)

Presenter: Mr MILLAS, Dimitrios (KU LEUVEN)



28th Texas Symp … / Report of Contributions H.E.S.S. Observations of the Large …


H.E.S.S. Observations of the Large Magellanic CloudMonday, December 14, 2015 2:00 PM (20 minutes)

The Large Magellanic Cloud (LMC) is an irregular satellite galaxy of the Milky Way, which hasbeen observed extensively at Very-High-Energy (VHE) gamma-rays with the H.E.S.S. telescopes,obtaining a deep exposure of 210 hours. In this talk we will present the results of this campaign.

Besides the already known PWN N 157B, these observations establish significant VHE gamma-rayemission from the super-bubble 30 Dor C and show evidence for emission from the supernovaremnant N 132D. It is the first unambiguous detection of gamma rays from a super-bubble and forthe first time individual cosmic-ray accelerators are identified in an external galaxy. Contrary totheoretical expectations, VHE gamma-ray emission is not detected from SN 1987A.

We will discuss these three objects, representing the high-energy tip of the VHE gamma-ray sourcepopulation in the LMC, as possible cosmic-ray accelerators, and compare them with similar sys-tems in our Galaxy. Further discoveries can be expected with more sensitive surveys of the LMCin gamma-rays, for instance with the Cherenkov Telescope Array.

Collaboration

H.E.S.S. Collaboration

Primary authors: LU, Chia-Chun (MPIK); AHARONIAN, Felix (MPIK Heidelberg, DIAS Dublin); VINK,Jacco (University of Amsterdam); RENAUD, Matthieu (LUPM); MAYER, Michael (Humboldt-Univer-sität zu Berlin); KOMIN, Nukri (Wits University); OHM, Stefan (DESY)

Presenter: KOMIN, Nukri (Wits University)



28th Texas Symp … / Report of Contributions Orbitally Modulated High-Energy …


Orbitally Modulated High-Energy Emission fromBlack Widows and Redbacks


Searches of unidentified Fermi sources have vastly expanded the number of known galactic-field“black widow” and “redback” circular MSP binary systems. We model the high-energy emissionfrom these systems due to relativistic leptons in the pulsar wind and those accelerated in intra-binary shocks. We show that the observed radio eclipses of the MSP can constrain the shockand system geometry. We also reproduce characteristic double-peaked orbitally modulated X-rayemission observed in many MSP binaries through Doppler boosting along the intrabinary shock.Redbacks and transitional pulsar systems, where the double-peaked X-ray light curve is observedat inferior conjunction, are suggested to be intrinsically different in shock geometry than otherMSP binaries. Inverse Compton emission as a function of energy and orbital phase, from electronsin the pulsar wind or intrabinary shock scattering UV photons from the irradiated companion, is ex-plored. The anticipated modulation of high-energy emission at the binary orbital period presents aunique astrophysical probe of the unknown physics of pulsar winds, relativistic shock accelerationand transport. Implications for Fermi-LAT and CTA target selection and searches are discussed.

Primary author: Dr WADIASINGH, Zorawar (Centre for Space Research, North-West Univer-sity)

Co-authors: Dr HARDING, Alice (NASA GSFC); VENTER, Christo (North-West University Potchef-stroom Campus); BOETTCHER, Markus (North-West University)

Presenter: Dr WADIASINGH, Zorawar (Centre for Space Research, North-West University)



28th Texas Symp … / Report of Contributions Indirect searches for dark matter in …


Indirect searches for dark matter in the gamma-raysky with the Fermi LAT status and prospects


Indirect dark matter (DM) searches rely on detection of stable by-products of DM interactions tosearch for a signal of this elusive component of the Universe. Among these final products, gammarays have recently played a major role in understanding the nature of the DM particle. This contri-bution reviews the current status of indirect DM searches with the Large Area Telescope, the maininstrument on board the Fermi gamma-ray space telescope. In the absence of any conclusive DMsignal, Fermi provides some of the most constraining DM limits obtained so far. Some prospectswith future data and/or instruments will also be presented.

Collaboration

Fermi LAT collaboration

Primary author: Dr COHEN-TANUGI, Johann (LUPM, Université de Montpellier & CNRS/IN2P3)

Presenter: Dr COHEN-TANUGI, Johann (LUPM, Université de Montpellier & CNRS/IN2P3)



28th Texas Symp … / Report of Contributions A new instability to black-hole spi …


A new instability to black-hole spin precessionThursday, December 17, 2015 2:20 PM (20 minutes)

We unveil a new dynamical instability in binary black holes with aligned spins. If the spin ofthe more massive black hole is aligned with the orbital angular momentum while the spin of theless massive black hole is anti-aligned, spins suddenly start to precess when the binary separationfalls below the threshold of our newly discovered instability. This instability provides a naturalchannel to circumvent astrophysical spin alignment at large binary separations allowing signifi-cant spin precession prior to merger. The onset of the instability lies in the sensitivity windows offuture detectors LIGO/Virgo and eLISA, thus predicting binaries that start precessing while beingobserved.

The instability criterion is derived with novel effective-potential methods to study the black-holebinary dynamics. We double average over both the orbital and the precessional timescale. Thisallows us to solve the post-Newtonian spin-precession equations analytically for arbitrary massratios and spins. These solutions improve our understanding of spin precession in much the sameway that the conical sections for Keplerian orbits provide additional insights beyond Newton’s1/r^2 law.

More on arXiv:1506.09116 (PRL).

Primary author: GEROSA, Davide (University of Cambridge)

Presenter: GEROSA, Davide (University of Cambridge)



28th Texas Symp … / Report of Contributions The Square Kilometre Array Obser …


The Square Kilometre Array Observatory: Prospectsfor Relativistic Astrophysics


The SKA is now in the detailed design phase with construction scheduled tobegin in early 2018, followed by early science from about 2020. A majorcomponent of its broad-ranging science program is focused on addressingquestions in fundamental physics. The current status of the project willbe summarised and the prospects for advancing relativistic astrophysicswill be highlighted.

Collaboration

SKA

Primary author: Dr BRAUN, Robert (SKA Organisation, Jodrell Bank Observatory)

Presenter: Dr BRAUN, Robert (SKA Organisation, Jodrell Bank Observatory)



28th Texas Symp … / Report of Contributions Exploring the TeV Universe with …


Exploring the TeV Universe with HAWCWednesday, December 16, 2015 3:15 PM (30 minutes)

The High Altitude Water Cherenkov (HAWC) observatory is an extensive air shower detector op-timized for studying gamma rays with energies between 100 GeV and 100 TeV.Located at an elevation of 4100 m near Puebla, Mexico, the array consists of 300 water tanks in-strumented with 4 photo-multiplier tubes each and was completed in March 2015.A wide instantaneous field of view of ~2 sr and a duty cycle >95% allow HAWC to survey 2/3 of thesky every day. These unique capabilities make it possible to perform an unprecedented survey ofTeV emission over most of the northern and part of the southern sky in order to map galactic andextra-galactic particle acceleration sites and search for gamma rays from dark matter annihilationand decay. HAWC is also ideally suited to monitor variable gamma-ray fluxes and search for flaresfrom active galactic nuclei, gamma-ray bursts, and other transient events, providing new insightsinto relativistic particle acceleration in astrophysical environments. We will present results fromthe first years of gamma-ray and cosmic-ray observations during the evolution of HAWC froma partial array to the completed observatory. Efforts to enhance our understanding of the highenergy Universe through multi-wavelength and multi-messenger analyses will also behighlighted.

Collaboration

HAWC Collaboration

Primary author: Dr LAUER, Robert (University of New Mexico)

Presenter: Dr LAUER, Robert (University of New Mexico)



28th Texas Symp … / Report of Contributions Law of Gravity, Structure and Geo …


Law of Gravity, Structure and Geometry of BlackHoles and the Universe

We shall present a blackhole theorem and a theorem on the structure of our Universe, proved in arecently published paper, based on 1) the Einstein general theory of relativity, and 2) the cosmolog-ical principle that the universe is homogeneous and isotropic. These two theorems are rigorouslyproved using astrophysical dynamical models coupling fluid dynamics and general relativity basedon a symmetry-breaking principle. With the new blackhole theorem, we further demonstrate thatboth supernovae explosion and AGN jets, as well as many astronomical phenomena including e.g.the recent reported are due to combined relativistic, magnetic and thermal effects. The radial tem-perature gradient causes vertical Benard type convection cells, and the relativistic viscous force(via electromagnetic, the weak and the strong interactions) gives rise to a huge explosive radialforce near the Schwarzschild radius, leading e.g. to supernovae explosion and AGN jets.

Primary author: Prof. WANG, Shouhong (Indiana University)

Co-author: Prof. MA, Tian (Sichuan U)

Presenter: Prof. WANG, Shouhong (Indiana University)


28th Texas Symp … / Report of Contributions Approximation of relevant elliptic …


Approximation of relevant elliptical equations in theSchwarzschild metric and some astrophysical

applicationsWednesday, December 16, 2015 4:35 PM (20 minutes)

In this talk I consider the light path of observed photons emitted by matter in a Schwarzschildgravitational field. Ray-tracing methods are employed to tackle this problem and the used mainequations are: light bending, time delay and solid angle. They are expressed through ellip-tic integrals that can be resolved numerically through generally complex routines. To run fastercodes and to deal more easily with the applications Beloborodov (2002) and Poutanen & Beloborodov(2006) found a simple polynomial approximation to describe respectively light bending and timedelay with high-accuracy for photon emitted at radius out of the event horizon (rrS = 2GM/c2).Though the results are relevant, it appears not clear how to derive them. I propose a mathematicalmethod able to recover the above equations and in addition to provide an analytical approxima-tion, for the first time, of the solid angle equation. Some applications show the power of this set ofapproximation equations like iron line profile and polarized light coming from an accretion disk.

Collaboration

Maurizio Falanga & Luigi Stella

Primary author: DE FALCO, Vittorio (University of Basel)

Co-author: Prof. FALANGA, Maurizio (International Space Science Institute (ISSI) Bern)

Presenter: DE FALCO, Vittorio (University of Basel)



28th Texas Symp … / Report of Contributions On stability of electroweak vacuu …


On stability of electroweak vacuum during inflationMonday, December 14, 2015 4:15 PM (20 minutes)

We study Coleman – De Luccia tunneling of the Standard Model Higgs field duringinflation in the case when the electroweak vacuum is metastable. We verify that thetunneling rate is exponentially suppressed. The main contribution to the suppressionis the same as in flat space-time. We analytically estimate the corrections due to theexpansion of the universe and an effective mass term in the Higgs potential that canbe present at inflation.

Primary author: SHKERIN, Andrey (EPFL)

Co-author: SIBIRYAKOV, Sergey (CERN & EPFL & INR RAS)

Presenter: SHKERIN, Andrey (EPFL)



28th Texas Symp … / Report of Contributions The Athena/X-IFU X-ray view of H …


The Athena/X-IFU X-ray view of Hot and EnergeticUniverse: probing the Black Hole environment


ESA’s Athena (Advanced Telescope for High-Energy Astrophysics) X-ray observatory mission, tobe launched in 2028, will revolutionise our knowledge of the hot and energetic Universe. The X-IFU (X-ray Integral Field Unit) is one of the two instruments on the focal plane of its large X-raytelescope, providing sensitive spatially resolved high-resolution spectroscopy. Athena/X-IFU willdeliver: (a) 3D mapping of hot cosmic gas through spatially resolved X-ray spectroscopy; (b) Weakspectroscopic line detection and (c) Physical characterization of the hot and energetic Universethrough plasma diagnostics, reverberation, line shapes, outflow/inflow spectral features etc. Incombination with the other Athena instrument, the WFI (Wide Field Imager), the X-IFU will beinstrumental in probing the physics around Black Holes in a range of spatial scales. In particular itwill measure Super-Massive Black Hole (SMBH) spins through Fe emission line shapes and thenceconstrain cosmic SMBH growth models; quantify the relationship between accretion and outflowsin galactic black holes and other compact sources; measure the mechanical energy of SMBH diskwinds and outflows through X-ray absorption features; probe the interaction of these winds andoutflows with their surroundings in local galaxies; and quantify the feedback produced by SMBHaccretion on galaxy cluster scales by measuring hot gas bulk motions and turbulence.

Primary author: BARCONS, Xavier (Instituto de Física de Cantabria (CSIC-UC))

Co-authors: BARRET, Didier (IRAP (UPS/CNRS)); Dr POINTECOUTEAU, Etienne (IRAP); Dr PIRO,Luigi (INAF/IAPS); DEN HERDER, jan-willem (SRON)

Presenter: BARCONS, Xavier (Instituto de Física de Cantabria (CSIC-UC))



28th Texas Symp … / Report of Contributions Lest we forget


Lest we forgetThursday, December 17, 2015 11:20 AM (20 minutes)

Astrophysics, both the name and the subject, was born in the halcyon days of irrational interna-tional exuberance near the end of the 19th century, when there were 100’s of international confer-ences in a decade and 10’s of new international organizations being established. Those includedthe French-inspired Carte du Ciel and G.E. Hale’s International Union for Solar Reseasch. GeneralRelativity; in contrast, came into being in 1915-16, in the darkest days of the Great War that hadalready put an end to the conferences and would soon abolish most of the organizations. Indeedan August 1914 eclipse expedition from Germany, which Einstein had asked to have a look forbending of statlight by the sun, was imprisoned in the Crimea almost immediately. As the warwent on, Karl SchwarIschild, on active duty, worked out his spherically symmetric solution to theEinstein equations, then died of war-related pemphigus.

On the astrophysics side, Henry Moseley, who had just put the periodic table into proper order in1913, died at Gallipoli in July, 1915 (and the Nobel Prize that surely should have been his went toCharles Barkla for 1917). Meanwhile, Paul Merrill learned to sensitize photographic plates for redand IR radiation (to penetrate haze during aerial reconnaissance), which Plates he later used todiscover Tc on stellar surfaces, thereby provided incontrovertible evidence that nuclear reactionswere occurring in their interiors (plus, of course, convection).

A conference among the winning countries held in London in 1918 declared that previously-existingscientific cooperative agreements should be terminated and new societies, involving only thosecountries “at war with the Central Powers” be formed. And 1919 saw both the founding of the Iliter-natienal Astronomical Union and the solar eclipse expeditions, organized by Eddington, which saythe bending of star light, at the predicted values which had doubled between Einstein initial 1911calculation and the definitive GR prediction of 1915-16.

Committee No. 1 of the IAU issieg Relativity, under the presidency of Eddington himself1/4 andthey voted themselves out of existence (under Levi.-Civita) in 1925 apparently on the grounds thatit had all be done. Indeed by then the “expected” gravitational redshifts had’been. reported inspectra of the sun (St. John 1923) and Sirius B (Adams 1 1925)./311th were wrong. High energyastrophysics and cosmology (that is, more or less, applications of SR and GR) did not return to theIAU until 1970 in Brighton UK.

Neutral Switzerland and the Netherlands, whose status had been guaranteed under the 1648 Treatyof Westphalia, adhered to the Union only in 1923 (though de Sitter was a VP from 1922) and Ger-many in 1952, with the Astronomisdhe Gesellschaft initially as the adhering organization for bothEast and West.

R. Gautier and M.G. Bkahuyzen (directors spectively of the Geneva and Leiden Observatories, hadattempted to bridge the Great War gap in geodetic observations with the Restricted (meaningneutrals only) Geodetic Association, which then folded into the new Unions by about 1928.

Primary author: Prof. TRIMBLE, Virginia (University of California Irvine)

Presenter: Prof. TRIMBLE, Virginia (University of California Irvine)



28th Texas Symp … / Report of Contributions Sub-Eddington accretion in neutro …


Sub-Eddington accretion in neutron star X-raybinaries


I will present our results of our studies on the spectral properties of neutron star low-mass X-ray binaries when they have accretion luminosities between 1e34 and 1e36 erg/s (roughly 0.01 -1 percent Eddington). We found that their photon index increases with decreasing 0.5-10 keV lu-minosity (the spectrum softens). Such behaviour has been reported for individual sources, but wenow demonstrate that likely most systems behave in a similar manner. When comparing withblack-hole systems, it is clear that most black-hole binaries have harder spectra at those luminosi-ties. This suggests that the spectral properties at low luminosities can be used to determine thenature of the accretor in unclassified binaries. We suggest that this difference likely arise from theneutron-star surface becoming dominantly visible. We also suggest that both the thermal compo-nent and the non-thermal component might be caused by low-level accretion on the neutron starsurface for luminosities below a few times 1e34 erg/s, contrary to the general believe.

Primary author: WIJNANDS, Rudy (University of Amsterdam)

Presenter: WIJNANDS, Rudy (University of Amsterdam)



28th Texas Symp … / Report of Contributions Cosmological constraints on the n …


Cosmological constraints on the neutron lifetimeMonday, December 14, 2015 5:15 PM (20 minutes)

We show how to derive new constraints on the neutron lifetime based on cosmological obser-vations. Under the assumption of standard Big Bang Nucleosynthesis, the abundance of light ele-ments, in particular Helium, is strongly dependent on the neutron lifetime. From CMB anisotropiesit is possible to constrain primordial abundances of light elements, inferring the value of the neu-tron lifetime. We start considering recent Planck 2015 results of temperature and polarizationanisotropies of the CMB. We show how including direct astrophysical measurements of primordialHelium abundance it is possible to obtain stringent constraints on the neutron lifetime. Further-more, we compute the neutron lifetime theoretical expectation and we compare this value withour results, with the value quoted by the Particle Data Group and with the ones obtained in bottlemethod” andbeam method” experiments. Finally, we perform forecasts on different future CMBexperiments. We highlight the high precision that can be reach from these experiments, such asCMB surveys as COrE+, in combination with a weak lensing survey as EUCLID, that could con-strain the neutron lifetime up to a ∼ 6 s precision.

Primary author: SALVATI, Laura (University of Rome, Sapienza)

Co-authors: MELCHIORRI, Alessandro (University of Rome, Sapienza); PAGANO, Luca (Universityof Rome, Sapienza); CONSIGLIO, Rossella (University of Naples, Federico II)

Presenter: SALVATI, Laura (University of Rome, Sapienza)



28th Texas Symp … / Report of Contributions Current constraints and forecasts o …


Current constraints and forecasts on the tilt andrunning of the primordial tensor spectrum


Gravitational waves can be produced by a wide range of astrophysical phenomena, such as inspiraland merging of neutron stars and black holes, supernova of massive stars, accreting neutron stars,etc. This talk is focused, instead, on a stochastic background of gravitational waves (GWs) ofcosmological origin, like the one predicted by inflation.

I start by considering a power law parametrization of the frequency spectrum of primordial tensormodes, with tiltnT and tensor-to-scalar ratio r. I discuss the constraints that can be placed on theseparameters by Cosmic Microwave Background (CMB) temperature and polarization anisotropiesalone, and then show how such constraints become stronger if one takes into account the contri-bution of gravitational waves to the radiation energy density. GWs add to the effective number ofrelativistic degrees of freedom Neff = 3.046 +NGW

eff , and then have an effect on the CMB angularspectra and the primordial abundances. More precisely, we find that the 95% CL limits on thetilt nT at a pivot scale of 0.01Mpc−1 go from nT = 1.7+2.1

−2.0 (Planck + BKP dataset, no NGWeff ) to

nT = 0.06+0.78−0.56 (with NGW

eff ).

In the second part of the talk I discuss the forecasts on a spectrum described by a spectral index nT

and its running nT,run: our analysis considers a future COrE-like satellite mission combined withdirect-detection experiments like AdvLIGO. When the contribution of primordial tensor modes toCMB spectral distortions of the µ-type is taken into account, we add the future measurements ofthe CMB spectrum by a PIXIE-like experiment.

For these forecasts two fiducial cosmologies are considered: at first a cosmology with no primordialgravitational waves, in order to see how well future experiments will be able to measure the tensorparameters. The second forecast takes as fiducial model one where the tensor-to-scalar ratio is oforder 10−2 (a value that can be reached by futuristic ground-based experiments such as AdvACT),and the tilt and running are fixed by the consistency relations of single-field slow-roll inflation.

In the final part of the talk, I discuss the implications of our results for models of single-field slow-roll inflation.

Primary author: Mr CABASS, Giovanni (Physics Department and INFN, “La Sapienza” Universityof Rome)

Co-authors: Mr MELCHIORRI, Alessandro (Physics Department and INFN, “La Sapienza” Univer-sity of Rome); Ms GIUSARMA, Elena (Physics Department and INFN, “La Sapienza” University ofRome); Ms SALVATI, Laura (Physics Department and INFN, “La Sapienza” University of Rome); MrPAGANO, Luca (Physics Department and INFN, “La Sapienza” University of Rome); Ms GERBINO,Martina (Physics Department and INFN, “La Sapienza” University of Rome)

Presenter: Mr CABASS, Giovanni (Physics Department and INFN, “La Sapienza” University ofRome)



28th Texas Symp … / Report of Contributions IGR J17361-4441: a possible planet …


IGR J17361-4441: a possible planetary tidaldisruption event in NGC 6388


In 2011 a new hard X-ray source, IGR J17361-4441, was discovered by INTEGRAL close the centreof the globular cluster NGC 6388.Based on its peak luminosity, it was classified as very faint X-ray transient.A Swift/XRT monitoring campaign showed an evident t^(-5/3) trend in the light curve,and a thermal emission of ~0.08 keV that did not evolve significantly with time.We investigated whether this source could be a tidal disruption event,and for certain assumptions, we found an accretion efficiency consistent with a massive whitedwarf and a disrupted minor body mass ~2E+27 M/M_Ch g in the terrestrial-icy planet regime.Although the density of white dwarfs and the number of free-floating planets are uncertain, weestimated the rate of planetary tidal disruptions in NGC 6388 to bein the range 3E-6 up to 3E-4 yr^(-1). Averaged over the 150 globular clusters in the Milky Way,the upper limit value corresponds to 0.05 yr^(-1), consistent with the life-time of INTEGRAL andSwift.

Primary author: Dr DEL SANTO, Melania (National Institute for Astrophysics - INAF)

Co-authors: Dr NUCITA, Achille (Università del Salento); Dr SEGRETO, Alberto (INAF); Prof.DE PAOLIS, Francesco (Università del Salento); Dr DE CESARE, Giovanni (INAF); Prof. LODATO,Giuseppe (Università degli Studi di Milano); Prof. FARIHI, Jay (University College London); Dr MANNI,Luigi (Università del salento)

Presenter: Dr DEL SANTO, Melania (National Institute for Astrophysics - INAF)



28th Texas Symp … / Report of Contributions General relativistic precession of o …


General relativistic precession of orbits around thestellar-mass black hole in H 1743-322


Accreting stellar mass black holes often show a quasi-periodic oscillation (QPO) in their X-ray fluxwith a period that slowly drifts from ~10s to ~0.05s and an iron emission line in their X-ray spec-trum. The iron line is generated by fluorescent re-emission, by the accretion disk, of X-ray photonsoriginating in the innermost hot flow. The line shape is distorted by relativistic motion of the orbit-ing plasma and the gravitational pull of the black hole. The QPO arises from the immediate vicinityof the black hole, but so far its physical origin has remained unknown. I will present observationsof the iron line in the black hole binary H 1743-322 where we find that the line energy varies quasi-periodically, in step with the ~4.5s QPO cycle. This result provides strong evidence that this classof QPO originates via Lense-Thirring precession, a General Relativistic effect causing the innerflow to precess as the spinning black hole twists up the surrounding space-time. This is the firstdemonstration of Lense-Thirring precession in the strong field regime of General Relativity. Theprecession occurs at a rate 14 orders of magnitude faster than in all previously reported examples,in the Earth’s gravitational field. Our result enables the application of tomographic techniques toprecisely map the motion of matter in the strong gravity near black hole event horizons.

Primary author: Dr INGRAM, Adam (University of Amsterdam)

Co-authors: Prof. DONE, Chris (University of Durham); Dr ALTAMIRANO, Diego (SouthamptonUniversity); Dr HEIL, Lucy (University of Amsterdam); Dr AXELSSON, Magnus (Tokyo Metropoli-tan University); Dr MIDDLETON, Matthew (Cambridge University); Prof. VAN DER KLIS, Michiel(University of Amsterdam); Dr UTTLEY, Phil (University of Amsterdam)

Presenter: Dr INGRAM, Adam (University of Amsterdam)



28th Texas Symp … / Report of Contributions The formation of primordial black …


The formation of primordial black hole dark matterWednesday, December 16, 2015 3:05 PM (20 minutes)

There are strong theoretical arguments which suggest that primordial black holes (PBHs) may haveformed from the collapse of large over-densities during the radiation dominated epoch shortly afterthe end of inflation. Because these black holes can form on much smaller scales than those visiblefrom the CMB or large-scale structure, they have historically been used to place a unique constrainton the amplitude of the small-scale primordial power spectrum.

In addition to their use in constraining the early universe, PBHs also represent a viable dark mattercandidate, and the conditions required for the formation of a large enough number of PBHs toconstitute dark matter will be discussed. A particular focus will be on a new method using CDMisocurvature perturbations arising from non-Gaussianity in the primordial universe. Isocurvatureperturbations produced in such a manner lead to extremely tight constraints on non-Gaussianity,and provides a powerful tool to distinguish between inflationary models which could lead to theformation of PBH dark matter.

Primary author: YOUNG, Sam (University of Sussex)

Co-author: BYRNES, Christian (University of Sussex (GB))

Presenter: YOUNG, Sam (University of Sussex)



28th Texas Symp … / Report of Contributions Magnetar formation from the mer …


Magnetar formation from the merger of binaryneutron stars


I will present results of recent investigations about the possibility to form long-lived or even stablemagnetars after the merger of a binary neutron star (BNS) system. BNSs are among the mostpowerful sources of gravitational waves (GWs) that will be detected by advanced LIGO and Virgo.While the inspiral GW signal is the main target for the first detections, the formation of a long-lived or even stable NS remnant after the merger can produce a long post-merger GW emissionthat could also be detected. Moreover magnetic fields can be strongly amplified during the mergerand this can lead to the formation of a magnetar. Large magnetic fields can have an impact onthe GW emission after merger and also lead to electromagnetic counterparts, such as the X-rayplateaus that are observed in short gamma-ray bursts. I will describe the dynamics that can leadto the formation of stable neutron stars after the merger of some BNS systems, how large magneticfields can be produced, and their possible effects on the GW signal.

Primary author: GIACOMAZZO, Bruno

Presenter: GIACOMAZZO, Bruno



28th Texas Symp … / Report of Contributions Lower limits on the magnetic field …


Lower limits on the magnetic field strength in theearly universe


Two recent estimates of lower limits for the stochastic primordial magnetic fields are reviewed.The first estimate pioneered by Neronov and Vovk (2010) is based on GeV-TeV γ-ray observationsof distant blazars by air-Cherenkov telecopes and the FERMI satellite. The generated e± pair beamsfrom double photon collisions with the extragalactic background light have been expected to initi-ate a full electromagnetic cascade as in vacuum. However, as the cascaded GeV inverse Comptonscattered gamma-rays have not been detected, the existence of small irregular intergalactic mag-netic fields, scattering the produced pairs, has been predicted. However, the generated initial pairbeams are subject to rapid electrostatic and electromagnetic kinetic plasma instabilities (Brodericket al. 2012, Schlickeiser et al. 2012) in the unmagnetized fully-ionized intergalactic medium, so thatless kinetic initial pair energy for the cascade emission is available, explaining the non-detectedGeV γ-rays.

The second estimate calculates the magnetic (and electric) equilibrium wavenumber spectrum ofaperiodic collective fluctuations in the thermal isotro\-pic electron-proton intergalactic plasma us-ing the generalized Kirchhoff laws, accounting self-consistently for the simultaneous competitionof spontaneous emission and absorption processes. By integrating the wavenumber spectrum overall wavenumber values provides for the total magnetic field strength in the IGM |δB| =

√(δB)2 ≃

10−17 G with maximum length scales≤ 1015 cm. This guaranteed magnetic field in the form of ran-domly distributed aperiodic fluctuations, produced by the spontaneous emission of the isotropicthermal IGM plasma, sets a robust lower limit on stochastic primordial magnetic fields, and servesas seed field for amplification by later possible plasma instabilities from anisotropic plasma particledistribution functions, MHD instabilities and/or the MHD dynamo process.

Primary author: Prof. SCHLICKEISER, Reinhard (Ruhr University Bochum, Germany)

Presenter: Prof. SCHLICKEISER, Reinhard (Ruhr University Bochum, Germany)

Session Classification: 10 - Cosmic magnetic fields


28th Texas Symp … / Report of Contributions Searching for new short-range for …


Searching for new short-range forces using opticallylevitated microspheres


We are developing a novel technique to search for non-Newtonian gravitational forces at micronlength scales using optically levitated dielectric microspheres. At high vacuum, dissipation of themicrosphere’s motion due to residual gas collisions becomes small, allowing sub-attonewton forcesensitivity. As a first demonstration of the ability to perform sensitive force measurements withthese techniques, we have searched for the presence of stable, millicharged particles bound in themicrospheres. These techniques can also enable searches for screened scalar particles, such asthe chameleon, which have been proposed to account for dark energy at cosmological distances,but which would also lead to detectable forces at distances below 100 µm. We will describe theexperimental apparatus, the results from the search for millicharged particles, and the expectedsensitivity of a search for non-Newtonian forces at micron length scales.

Primary author: MOORE, David (Stanford University)

Co-authors: RIDER, Alexander (Stanford University); BLAKEMORE, Charles (Stanford Univer-sity); GRATTA, Giorgio (Stanford University); LU, Marie (Stanford University); LOUIS, Maxime (Ecolepolytechnique, Universite Paris-Saclay); KURINSKY, Noah (Stanford University)

Presenter: MOORE, David (Stanford University)



28th Texas Symp … / Report of Contributions Quasi-periodic oscillations of pert …


Quasi-periodic oscillations of perturbed toriWednesday, December 16, 2015 3:42 PM (3 minutes)

Our research focuses on axisymmetric hydrodynamical simulations. The models implementedare thinner tori and thicker torus in equilibrium around a non-rotating black hole. The tori wereconstructed with a constant distribution of angular momentum obtained from Kluzniak-Lee (apseudo-Newtonian) potential. Epicyclic motion were triggered by adding sub-sonic velocity fields;radial, vertical and diagonal. As the perturbed tori evolved in time, we measured L2 norm ofdensity and obtained the power spectrum which manifested modes as predicted by theory. Resultsfrom our simulations are relevant in the context of high-frequency quasi-periodic oscillations (HFQPOs) observed in stellar-mass black hole binaries.

Collaboration

Varadarajan Parthasarathy, Wlodek Kluzniak, Antonios Manousakis

Primary author: Mr PARTHASARATHY, Varadarajan (N. Copernicus Astronomical Center)

Presenter: Mr PARTHASARATHY, Varadarajan (N. Copernicus Astronomical Center)



28th Texas Symp … / Report of Contributions Is there evidence for anisotropy in …


Is there evidence for anisotropy in CMB data?Monday, December 14, 2015 4:35 PM (20 minutes)

Large scales in the Cosmic Microwave Background (CMB) may break statistical isotropy. Bianchimodels are often invoked as a possible explanation for these low-\ell features: they provide ananisotropic underlying pattern over which the usual stochastic fluctuations are superimposed.However, the Bianchi models generally employed in the analysis of CMB data — despite mim-icking the anomalies in the CMB temperature map — overproduce B-mode polarisation due to thevery specific way in which they break isotropy.

In this work, we consider the most general way to break Friedmann-Robertson-Walker isotropythat still preserves homogeneity and test for its signatures in Planck temperature and polarisationmap; WMAP data are also analysed for comparison. In addition to the well-known Bianchi modelsthat are more commonly employed in the literature, we consider more physical and untested-forBianchi models that comply with polarisation constraints. We also show that improved constraintson anisotropy may be obtained by extending the likelihood to high \ell. Nested sampling tech-niques are employed to determine whether the Bayesian evidence favours anisotropic universesover the standard Lambda-CDM scenario.

Primary author: Ms SAADEH, Daniela (University College London)

Co-authors: Dr PONTZEN, Andrew (University College London); Prof. PEIRIS, Hiranya (Uni-versity College London); Dr MCEWEN, Jason (Mullard Space Science Laboratory, University CollegeLondon); Dr FEENEY, Stephen (Imperial College London)

Presenter: Ms SAADEH, Daniela (University College London)



28th Texas Symp … / Report of Contributions The fate of Super Massive Black H …


The fate of Super Massive Black Holes in galaxymergersWednesday, December 16, 2015 4:55 PM (20 minutes)

We study numerically the fate of SMBHs in galaxy mergers. If the galaxies involved in thesemergers have a gas fraction of at least %1 is expected that a massive gaseous disk with a massof ten to hundred times the mass of the SMBHs will be formed in the central kilo parsec of themerger remnant. The SMBHs in these nuclear region will form a SMBH binary which separationwill shrink mainly due to the gravitational torque produced by the gaseous disk. We focus ourstudy in the transport of angular momentum from the binary to the disk and how this transportcan result on the formation of a gap in the gaseous disk. If the formation of such gap occurs theshrinking of the SMBH binary will be dramatically delayed, instead if the binary doesn’t excavate agap on the disk the shrinking of the binary will continue until the extraction of angular momentumdue to the emission of gravitational waves becomes efficient enough to drive the final coalescenceof the binary.We find in all our simulations of galaxy mergers that the formation of such a gap is unlikely andwill be possible only if the SMBH binary mass is comparable or much greater than the mass of thegaseous disk. Our simulations imply that the mass of the SMBHs must be at least of the order of1010 M⊙, which is larger than the mass of the most massive SMBHs harbour by giant ellipticalgalaxies or cD galaxies. Our results have important implication on the number of SMBHs that willexperience a fast migration and will enter in the gravitational wave emission regime, estimationthat it is crucial to determine the amount of gravitational waves that we expect to observe withthe future mission eLISA.

Primary authors: Prof. ESCALA, Andres (Universidad de Chile); Mr DEL VALLE, Luciano (Uni-versidad de Chile)

Presenter: Prof. ESCALA, Andres (Universidad de Chile)



28th Texas Symp … / Report of Contributions Cosmological mass transport on g …


Cosmological mass transport on galactic nuclei andthe formation of high redshift quasars.


By using AMR cosmological hydrodynamic N-body zoom-in simulations, with the RAMSES code,we studied the mass transport processes onto galactic nuclei from high redshift up to z~6. Dueto the large dynamical range of the simulations we were able to study the mass accretion processon scales from ~50 kpc to ~pc. The SMBHs are modelled as a sink particles at the center of ourgalaxies, which allowed us to quantify the BH growth in relation with the mass transport processesassociated to three differentangular momentum fluxes: i) Reynolds stress, ii) gravitational stress and iii) viscous stress. Sucha quantification allowed us to identify the main mass transport process as a function of the scalesof the problem. We found that in simulations that include radiative cooling and SNe feedback, theSMBH grows at theEddington limit most of the time. The disk momentum flux is dominated by the Reynoldsstress transporting mass at a rate of ~1-10 Msun/yr. This level of SMBHs accretion rates found inour cosmological simulation, are needed in all models of SMBH growth attempted to explain theformation of redshift 6-7 quasars.

Primary authors: Dr PRIETO, Joaquin (Universidad de Chile); Prof. ESCALA, andres (Universidadde chile)

Presenter: Prof. ESCALA, andres (Universidad de chile)



28th Texas Symp … / Report of Contributions Formation of discs around super- …


Formation of discs around super-massive black holebinaries from infalling clouds

There is compelling evidence that most -if not all- galaxies harbour a super-massive black hole(SMBH) at their nucleus, hence binaries of these massive objects are an inevitable product of thehierarchical evolution of structures in the universe, and represent an important but thus-far elusivephase of galaxy evolution. Gas accretion via a circumbinary disc is thought to be important forthe dynamical evolution of SMBH binaries, as well as in producing luminous emission that can beused to infer their properties. One plausible source of the gaseous fuel is clumps of gas formeddue to turbulence and gravitational instabilities in the interstellar medium, that later fall towardand interact with the binary. In this context, we model numerically the evolution of turbulentclouds in near-radial infall onto equal-mass SMBH binaries, using a modified version of the SPHcode GADGET-3. We present a total of 12 simulations that explore different possible pericentredistances and relative inclinations, and show that the formation of circumbinary discs and discsaround each SMBH (’mini-discs’) depend on those parameters. We also study the dynamics of theformed discs, and the variability of the feeding rate onto the SMBHs in the different configurations.

Primary author: GARRIDO GOICOVIC, Felipe (Instituto de Astrofisica, PUC, Chile)

Co-authors: Dr SESANA, Alberto (School of Physics and Astronomy, University of Birmingham); DrSTASYSZYN, Federico (Leibniz-Institut für Astrophysik Potsdam); Dr CUADRA, Jorge (Instituto deAstrofísica, PUC, Chile); Dr AMARO-SEOANE, Pau (Max-Plank-Institut für Gravitationsphysik); DrTANAKA, Takamitsu (Stony Brook University)

Presenter: GARRIDO GOICOVIC, Felipe (Instituto de Astrofisica, PUC, Chile)


28th Texas Symp … / Report of Contributions Correlated neutrino and photon e …


Correlated neutrino and photon emission duringγ-ray flares from the blazar Mrk 421


Blazars, being highly variable sources across the electromagnetic spectrum, may serve as promis-ing targets for high-energy neutrino detection, especially during periods of flaring activity. Usingas a testbed the nearby blazar Mrk 421, we present a detailed hadronic model of its emission duringa 13-day flare in 2010 with unprecedented multi-wavelength and temporal coverage. We calculatethe expected muon neutrino event rate observed by IceCube at energies >1 PeV, and compare itwith that expected from a longer, yet non-flaring, period of emission. After applying the derivedcorrelation between the >1 PeV neutrino and 0.1-300 GeV emission to the long-term Fermi/LATlight curve of Mrk 421, we calculate the expected number of muon neutrino events above 1 PeVwithin 5 years of full IceCube detector livetime and discuss the implications of the results.

Primary author: Dr PETROPOULOU, Maria (Purdue University)

Co-authors: Dr DIMITRAKOUDIS, Stavros (University of Alberta); Mr COENDERS, Stefan (Tech-nische Universitaet Muenchen)

Presenter: Dr PETROPOULOU, Maria (Purdue University)



28th Texas Symp … / Report of Contributions Disks and jets


Disks and jetsFriday, December 18, 2015 11:55 AM (35 minutes)

After reviewing the physics of jet formation by accreting black holes, I will present the resultsof recent 3D general relativistic magnetized fluid dynamics simulations and discuss the insightsthey give us into the disk-jet connection. I will finish by presenting the simulated spectra andimages and the constraints on the near event horizon physics coming from the comparison to theobservations of the supermassive black hole at the center of our galaxy.

Primary author: TCHEKHOVSKOY, Alexander (Uiversity of California Berkeley)

Presenter: TCHEKHOVSKOY, Alexander (Uiversity of California Berkeley)



28th Texas Symp … / Report of Contributions The LHC and the Universe


The LHC and the UniverseWednesday, December 16, 2015 11:55 AM (35 minutes)

From the discovery of the Higgs boson to constraints on dark-matter interactions and on new-physics effects, the LHC run at 8 TeV has contributed greatly to our knowledge of the particlephysics world. I will highlight how this knowledge is influencing advancements in the physics ofthe early universe and how the interplay between particle physics and cosmology will progresswith the 13 TeV LHC run.

Primary author: GIUDICE, Gian (CERN)

Presenter: GIUDICE, Gian (CERN)



28th Texas Symp … / Report of Contributions Relaxing the limits on inflationary …


Relaxing the limits on inflationary magnetogenesisWednesday, December 16, 2015 2:00 PM (21 minutes)

Inflation has long been thought as the best way of producing large-scale primordial magnetic fields.To achieve fields strong enough to seed the galactic dynamo, most of the generation mechanismsoperate outside conventional electromagnetic theory, which is typically restored after the endof the de Sitter phase. Breaking away from standard electromagnetism can lead to substantiallystronger magnetic fields at the end of inflation and thus compensate for their subsequent adiabaticdepletion. We argue that the drastic magnetic enhancements during the de Sitter era may not benecessary. In particular, we use causality arguments to claim that, contrary to the common belief,superhorizon-sized magnetic fields are not necessarily frozen into the matter after inflation. Onthese super-Hubble scales the magnetic decay can slow down considerably, and thus make it mucheasier to produce primordial fields of astrophysical interest today.

Primary author: TSAGAS, Christos (Aristotle University of Thessaloniki)

Presenter: TSAGAS, Christos (Aristotle University of Thessaloniki)



28th Texas Symp … / Report of Contributions Thick tori and flows around rotati …


Thick tori and flows around rotating boson starsThursday, December 17, 2015 5:38 PM (21 minutes)

Accretion disks play an important role in the evolution of their relativistic inner compact objects.The emergence of a new generation of interferometers will allow resolving these accretion disksand providing more information about the properties of the central gravitating object. Due to thisinstrumental leap forward it is crucial to investigate the accretion disk physics near various typesof inner compact objects now to deduce later constraints on the central objects from observations.A possible candidate for the inner object is the boson star. Here, we will present the differencesbetween accretion structures surrounding boson stars and black holes. We show that the accretiontori around boson stars have different characteristics than in the vicinity of a black hole. Withfuture instruments it could be possible to use these differences to constrain the nature of compactobjects.

Primary author: MELIANI, Zakaria (LUTH, Observatoire de Paris)

Presenter: MELIANI, Zakaria (LUTH, Observatoire de Paris)



28th Texas Symp … / Report of Contributions Diagnose the Sources of IceCube N …


Diagnose the Sources of IceCube Neutrinos withFermi Observation


The origin of IceCube detected diffuse neutrinos is still unknown. Searching for their sources alsohelps to solve the problem of the cosmic ray orgigin. We assume that there is connection betweenthe neutrino and gamma-ray fluxes from the sources. It holds if both the neutrinos and gamma-rays are haronic origin. Moreover, it should also hold in statistic sense even if the gamma-raysare leptonic origin because the ratio of the energy carried by electrons and cosmic rays may beroughly constant. By the neutrino-gamma connection, we use Fermi observations of various can-didate sources to constrain the diffuse neutrino origin. We find that the Galactic diffuse neutrinoemission contributes less than 10% of the IceCube flux, and point sources cannot account for theIceCube neutrinos either; as for extragalactic candidate sources, neither gamma-ray bursts nor ac-tive galactic neuclei jets contribute more than 10%, whereas starburst galaxies may be a promisesource for IceCube neutrinos.

Primary author: LI, Zhuo (Peking University)

Presenter: LI, Zhuo (Peking University)



28th Texas Symp … / Report of Contributions Constraints on a DE parametrizati …


Constraints on a DE parametrization using BAO andForecasting for future surveys


For this work a parametrization for the Dark Energy (DE) equation of state is proposed and tested.

We derive constraints on our state equation parameters from the baryon acoustic oscillation (BAO)measurements. In particular we take advantage of high precision BAO measurements from galaxyclustering and the Lymann-α forest in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS).

Our analysis lead us to propose a DE fluid featuring a transition from a high redshift value ofwi(z ≫ 0)= - 0.96 to a w0=-0.93 value at z = 0. The transition redshift is constrained to be as highas zT = 1.83.

We find a good agreement of our model to the data, having a χ2red = 1.03.

Given the upmost importance of designing the future DE experiments (such as DESI) we provide asimple statistical analysis to forecast the required reduction in observational errors to distinguishbetween a Cosmological constant scenario and a time evolving DE model. Specifically we find thata reduction of 11% on the associated errors to rBAO(z) observational measurements is enough toexclude a cosmological constant at 1σ of statistical significance in favor to our model and a 41%reduction would exclude the cosmological constant at 2σ level.

Primary authors: Dr DE LA MACORRA, Axel (Physics Department - National University of Mexico(UNAM)); Ms JABER, Mariana (Universidad Nacional Autónoma de México)

Presenter: Ms JABER, Mariana (Universidad Nacional Autónoma de México)



28th Texas Symp … / Report of Contributions Tensions Between CMB and Weak …


Tensions Between CMB and Weak Lensing Data Setswhen Testing General Relativity


There has been quite a bit of recent discussion about tension between CMB and weak lensingdata sets, especially in the context of testing general relativity using modified growth parameters.We use a combination of cosmological data sets, including the CMB temperature anisotropy datafrom Planck, weak lensing tomography from CFHTLenS, and the WiggleZ galaxy power spectrumto place constraints on modified growth parameters. A likelihood analysis is performed usingthe publicly available package ISiTGR. We explore what tensions, if any, are present between theCMB and weak-lensing data when using three different parameterizations for the modified growthparameters.

Primary author: DOSSETT, Jason (INAF - Osservatorio Astronomico di Brera)

Co-authors: PARKINSON, David (University of Queensland); ISHAK, Mustapha (The University ofTexas at Dallas); DAVIS, Tamara (University of Queensland)

Presenter: DOSSETT, Jason (INAF - Osservatorio Astronomico di Brera)



28th Texas Symp … / Report of Contributions Galactic magnetic fields


Galactic magnetic fieldsTuesday, December 15, 2015 2:25 PM (20 minutes)

This talk will provide an overview of our current knowledge about galactic magnetic fields. Thetypical properties of magnetic fields in galactic discs and halos will be described as well as magneticfield characteristics at different length scales between 10 pc and 10 kpc. The talk will concentrateon reviewing what is known from observations, but will also point out the areas where theoreticalmodels have been successful and where they still face challenges. I will briefly discuss the prospectsfor exciting new developments in our understanding of galactic magnetic fields and their evolution,due to the improvement in radio telescope capabilities that is currently underway.

Primary author: FLETCHER, Andrew

Presenter: FLETCHER, Andrew



28th Texas Symp … / Report of Contributions Luminosity dependent change of t …


Luminosity dependent change of the emissiondiagram in the X-ray pulsar 4U 1626-67


We have discovered strong indications of a correlation between the appearance of the Fe Kα emis-sion line in the spectrum of the X-ray pulsar 4U 1626-67 and its luminosity and shape of its pulseprofile. Spectroscopic analysis of the latest, simultaneous Chandra/RXTE observation of 4U 1626-67, revealed the presence of a narrow Fe Kα emission line. The observation was performed whenthe source was in a high luminosity (> 10^37 erg/s) state. This feature was not present in previousChandra and XMM-Newton observations, performed when the source was in a low luminosityregime. Timing analysis of archival XMM-Newton and RXTE data also revealed a major change inthe pulse profile of the source. Namely, the pulse profile during the Chandra/RXTE, high luminos-ity, observation has a characteristic double peaked shape that is radically different from the pulseprofile during the XMM-Newton observation when the luminosity was lower and the Fe line wasnot present.

The iron line parameters are consistent with reflection of X-ray radiation off an accretion disktruncated close to the magnetospheric radius of a high field pulsar (B~10^12 Gauss). Furthermore,using our X-ray diagnostics method (Koliopanos et al. 2013 [1]), we showed that the relativefaintness of the emission line, is consistent with reflection off a C/O rich disk, as expected for thissystem. We argue that the appearance of the line and the change in the shape of the pulse profileare correlated and are the result of a major modification of the emission diagram of the accretioncolumn, from a pencil beam to a fan beam pattern. This change was caused by an increase inthe mass accretion rate, as was theoretically predicted by Basko & Sunyaev in 1976 [2]. To ourknowledge, this is the first time this combination of events has been reported and it opens up thepossibility of observing similar events in other X-ray pulsars.

References

[1] Koliopanos F., Gilfanov M., Bildsten L., 2013, MNRAS, 432, 1264

[2] Basko M. M., Sunyaev R. A., 1976, MNRAS, 175, 395

Primary author: Dr KOLIOPANOS, Filippos (Research Institute in Astrophysics and Planetology(IRAP), Toulouse, France)

Co-author: Dr GILFANOV, Marat (Max Planck Institute for Astrophysics, Space Research Instituteof Russian Academy of Sciences)

Presenter: Dr KOLIOPANOS, Filippos (Research Institute in Astrophysics and Planetology (IRAP),Toulouse, France)



28th Texas Symp … / Report of Contributions How accreting black holes may sh …


How accreting black holes may shape theirsurroundings through AGN feedback


Black holes in active galactic nuclei (AGN) respond to the accretion process by feeding back en-ergy and momentum into the surroundings. Such AGN feedback is generally invoked to quenchstar formation in host galaxies, either by heating or removing the ambient gas. However, feedbackfrom the accreting black hole may also play other roles in galaxy evolution.We consider the roleof radiation pressure on dust in driving outflows on galactic scales, and the possibility of AGNfeedback triggering star formation within those feedback-driven outflows. In this picture, the ac-creting black hole is responsible for both driving star formation in the galaxy (”positive feedback”),as well as clearing dusty gas out of the host (”negative feedback”). I will discuss how the centralblack hole may shape not only the development of its own host galaxy, but also the evolution ofthe whole surrounding environment.

Primary author: Dr ISHIBASHI, Wako (ETH Zurich)

Co-author: Prof. FABIAN, Andrew (University of Cambridge)

Presenter: Dr ISHIBASHI, Wako (ETH Zurich)



28th Texas Symp … / Report of Contributions Aspects of infrared non-local modi …


Aspects of infrared non-local modifications ofGeneral Relativity


We introduce some recently proposed non-local infrared modifications of general relativity. Wediscuss which are the motivations to introduce non-localities in a theory of gravity. We thenpresent a particular class of models which has been recently shown to be cosmologically viable,with an extremely good compatibility with cosmological data. We present the general features ofsuch a class of non-local models and we briefly review some recent developments in the under-standing of the nature of non-localities.

Primary author: Ms CUSIN, Giulia (University of Geneva)

Co-authors: Prof. MAGGIORE, Michele (University of Geneva); Dr FOFFA, Stefano (University ofGeneva)

Presenter: Ms CUSIN, Giulia (University of Geneva)



28th Texas Symp … / Report of Contributions Multiwavelength observations of …


Multiwavelength observations of gamma-ray loudbinaries


Gamma-ray loud binaries are are a recently identified class of X-ray binaries in which interactionof an outflow from the compact object (black hole or neutron star) with the wind and radiationemitted by a companion star leads to the production of very-high energy (VHE) gamma-ray emis-sion. Only five systems have been firmly detected so far as persistent or regularly variable TeVgamma-ray emitters. Detailed studies of the broadband spectral and timing properties of thesesources are crucial for understanding the nature of these peculiar objects. In my talk I will reviewthe outcome of extensive multiwavelength observations of the 2014 PSR B1259-63 periastron pas-sage, which shed a light on the nature of the puzzling GeV flare from the system, and also discusswhat can we learn from the numerous X-ray observations of LSI +61 303 performed the last decadeby SWIFT, Suzaku, XMM and Chandra satellites.

Primary author: CHERNYAKOVA, Maria (DCU)

Co-authors: Dr NERONOV, Andrii (ISDC); Mr MALYSHEV, Denys (ISDC); Dr VOVK, Ievgen(MPG); Mr BABYK, Iurii (DCU); Dr TSYGANKOV, Sergey (Tuorla Observatory)

Presenter: CHERNYAKOVA, Maria (DCU)



28th Texas Symp … / Report of Contributions The role of general relativity and r …


The role of general relativity and reconnection inpulsar radiation


Pulsars shine throughout the electromagnetic spectrum, from radio waves to energetic gammarays. The radio emission is thought to originate from the discharge of the polar-cap and the for-mation of copious electron-positron pairs. Gamma rays are traditionally associated with parti-cle acceleration in electrostatic gaps within the light cylinder. The recent development of globalParticle-In-Cell (PIC) simulations of the pulsar magnetosphere enables to test these scenarios self-consistently. We show that general relativistic effects, most notably frame-dragging, are essentialto ignite pair creation in the polar cap for low-inclination pulsars, and hence enable pulsars to emitradio waves. In addition, three-dimensional radiative PIC simulations indicate that the currentsheet that forms beyond the light cylinder is the main site of particle acceleration in plasma-filledpulsars, instead of gaps within the co-rotating magnetosphere. Relativistic reconnection dissipatesthe magnetic energy which is then converted to energetic particles and high-energy synchrotronradiation. We present self-consistent modeling of pulsar gamma-ray lightcurves and spectra ob-tained directly from the kinetic simulations, and discuss the results in the context of observedgamma-ray pulsars.

Primary author: CERUTTI, Benoit (Princeton University)

Co-authors: PHILIPPOV, Alexander (Princeton University); SPITKOVSKY, Anatoly (Princeton Uni-versity)

Presenter: CERUTTI, Benoit (Princeton University)



28th Texas Symp … / Report of Contributions Exploring the consequences of par …


Exploring the consequences of parameter values incosmological models with CosmoEJS, an interactive

package of cosmology Java simulationsMonday, December 14, 2015 6:02 PM (3 minutes)

It is not only important to constrain the parameters of cosmological models with the most recentand precise observations, but it is also crucial to understand the physical consequences of those pa-rameters for the different, but complimentary observations involved. CosmoEJS is an interactiveJava package of simulations that allow the user to explore the ramifications of choosing variousvalues for the cosmological parameters of a particular model. These simulations now include ob-servations of the growth of structures of galaxies, as well as, the expansion history of the universe.Users can visually inspect the plotted theoretical values of their model, compare numerical fittingusing χ2 values, calculate derived cosmological values, and finally plot the expansion trajectoryof their models as they evolve in time.

Primary author: MOLDENHAUER, Jacob (University of Dallas)

Co-authors: CAVANNA, Francis (University of Dallas); O’TOOLE, William (University of Dal-las); ZIMMERMAN, William (University of Dallas)

Presenter: MOLDENHAUER, Jacob (University of Dallas)



28th Texas Symp … / Report of Contributions Testing varying speed of light cos …


Testing varying speed of light cosmologies in futureexperiments.


In this talk I will briefly present the advantages and drawbacks of varying speed of light c cosmolo-gies and relate them to the of varying fine structure constant α theories. Then, I will discuss somenew tests (redshift drift and angular diameter distance maximum against Hubble function) whichmay allow measuring timely and possibly even spatial change of the speed of light. The criteria todetect 1% variability of c by mock data for future missions such as Euclid and SKA (Square Kilo-meter Array) will be given.Literature:1. A. Balcerzak, M.P. Dąbrowski, Redshift drift in varying speed of light cosmology, Physics LettersB728, 15-18 (2014).2. V. Salzano, M.P. Dąbrowski, R. Lazkoz, Measuring the speed of light with Baryon Acoustic Os-cillations, Physical Review Letters 114, 101304 (2015).3. M.P. Dąbrowski, A. Balcerzak, V. Salzano – in progress.

Primary author: DABROWSKI, Mariusz (University of Szczecin)

Co-authors: Dr BALCERZAK, Adam (University of Szczecin); Dr SALZANO, Vincenzo (Universityof Szczecin)

Presenter: DABROWSKI, Mariusz (University of Szczecin)



28th Texas Symp … / Report of Contributions Asymptotic evolution of Robinson- …


Asymptotic evolution of Robinson-Trautmanspacetimes


By exploring the numerical scheme introduce in [1], we analyze the asymptotic (u → ∞) evolutionof Robinson-Trautman spacetimes, with special emphasis on the behavior of the apparent horizonand its curvature anisotropies, which can indeed induce accelerations and a recoil in the remnantblack hole due to asymmetrical emission of gravitational waves [2].

References

[1] A. Saa and R.P. Macedo, Gravitational wave recoil in Robinson-Trautman spacetimes, Phys. Rev.D78, 104025 (2008) [arXiv:0809.3039].

[2] L. Rezzolla, R.P. Macedo, J.L. Jaramillo, Understanding the “anti-kick” in the merger of binaryblack holes, Phys. Rev. Lett. 104, 221101 (2010) [arXiv:1003.0873].

Primary author: SAA, Alberto (UNICAMP)

Presenter: SAA, Alberto (UNICAMP)



28th Texas Symp … / Report of Contributions Inhomogeneous conformally flat …


Inhomogeneous conformally flat models of theuniverse


I will discuss the benefits of the conformally flat inhomogeneous pressure models of the universe.Then, I will present the results of checking these models against supernovae data for off-centersobservers and against other data (BAO, CMB) for the centrally-placed observers. I will also com-ment on the possible advantage of these models in view of the recently given Green and Waldconditions for backreaction to mimic dark energy.

1. A. Balcerzak, M.P. Dąbrowski, and T. Denkiewicz, Off-center observers versus supernovaein inhomogeneous pressure universes, Astroph. Journ. 792, 92-99 (2014).

2. A. Balcerzak, M.P. Dąbrowski, T. Denkiewicz, D. Polarski, D. Puy, A critical assessment ofsome inhomogeneous pressure Stephani models, Phys. Rev. D91, 083506 (2015).

3. A. Balcerzak, M.P. Dąbrowski - in progress.

Primary author: DABROWSKI, Mariusz (University of Szczecin)

Co-author: Dr BALCERZAK, Adam (University of Szczecin)

Presenter: DABROWSKI, Mariusz (University of Szczecin)



28th Texas Symp … / Report of Contributions Astrophysical Boundary Layers: A …


Astrophysical Boundary Layers: A New PictureThursday, December 17, 2015 6:19 PM (20 minutes)

Accretion is a ubiquitous process in astrophysics. In cases when the magnetic field is not too strongand a disk is formed, accretion can proceed through the mid plane all the way to the surface ofthe central compact object. Unless that compact object is a black hole, a boundary layer will beformed where the accretion disk touches its surfaces. The boundary layer is both dynamically andobservationally significant as up to half of the accretion energy is dissipated there.

Using a combination of analytical theory and computer simulations we show that angular momen-tum transport and accretion in the boundary layer is mediated by waves. This breaks with thestandard astrophysical paradigm of an anomalous turbulent viscosity that drives accretion. How-ever, wave-mediated angular momentum transport is a natural consequence of “sonic instability.”The sonic instability, which we describe analytically and observe in our simulations, is a closecousin of the Papaloizou-Pringle instability. However, it is very vigorous in the boundary layerdue to the immense radial velocity shear present at the equator.

Our results are applicable to accreting neutron stars, white dwarfs, protostars, and protoplanets.

Collaboration

Roman Rafikov, James Stone

Primary author: BELYAEV, Mikhail (UC Berkeley/TAC)

Co-authors: Prof. STONE, James (Princeton University); Prof. RAFIKOV, Roman (Princeton Uni-versity)

Presenter: BELYAEV, Mikhail (UC Berkeley/TAC)



28th Texas Symp … / Report of Contributions The radial velocity profile of the fi …


The radial velocity profile of the filament galaxies inthe vicinity of the Virgo cluster as a test of gravity


The radial velocities of the galaxies in the vicinity of a massive cluster shows deviation from thepure Hubble flow due to their gravitational interaction with the cluster. According to a recentstudy of Falco et al. with a high-resolution N-body simulation based on General Relativity (GR),the radial velocity profile of the galaxies located at distances larger than three times the virial radiusof a neighbour cluster has a universal shape and could be reconstructed from direct observablesprovided that the galaxies are distributed along one dimensional filament. Analyzing the narrowfilamentary structure identified by Kim et al. in the vicinity of the Virgo cluster from the NASA-Sloan-Atlas catalog, we reconstruct the radial velocity profile of the Virgo filament galaxies andcompare it with the universal formula derived by Falco et al. It is found that unless the virial massof the Virgo cluster exceeds 1015h−1M the universal formula fails to describe the reconstructedradial velocity profile whose peculiar velocity term turns out to decrease much less rapidly. Spec-ulating that the disagreement between the GR prediction and the observed radial velocity profileof the Virgo filament galaxies may be due to the presence of unscreened fifth force, we suggest theradial velocity profile of the filament galaxies around the clusters as a powerful test of gravity onthe cosmological scale.

Collaboration

Jounghun Lee, Suk Kim, Soo-Chang Rey

Primary author: Prof. LEE, Jounghun (Seoul National University)

Presenter: Prof. LEE, Jounghun (Seoul National University)



28th Texas Symp … / Report of Contributions Tidal disruption events induced by …


Tidal disruption events induced by the Kozai-Lidovmechanism


We geometrically analyze the evolution of the Kozai-Lidov mechanism induced by an infallingtertiary. This approach enables us to clearly understand how the inner orbits are deformed, inresponse to the time variation of the related phase-space structure.We predict that, in a stellar cluster associated with massive black hole binaries, a constituent starcould abruptly become highly eccentric, because of a peculiar bifurcation pattern.

Primary author: SETO, Naoki

Co-author: IWASA, Mao (Kyoto University)

Presenter: SETO, Naoki



28th Texas Symp … / Report of Contributions Viability of a quintessence model …


Viability of a quintessence model with inverse powerlaw potential as a dark energy candidate


The physical explanation of the dark energy as the responsible agent of the currently acceleratedexpansion of the Universe remains as one of the most challenging questions of the modern physcis.Besides the standard scenario (in which it is caused by a cosmological constant) there are otherproposals which range from the introduction of new more or less exotic components, to modifica-tions to the general relativity theory. Among these proposals, some quintessence models possesthe desirable feature of being free of fine-tuning problems showing a dynamical behaviour clearlydiscernible from the LCDM model. In this poster we present an inverse-power-law-potentialquintessence model inspired by a dynamically condensed Affleck-Dine-Seiberg superpotential. Weshow the basic phenomelogy predicted by this model and give contrains for its parameters usingCMB information -WMAP 9yr & Planck- as well as supernovae Ia and BAO recent observations.

Primary author: Mr ALMARAZ AVIÑA, Erick Jonathan (Instituto de Física / UNAM)

Co-author: Dr DE LA MACORRA, Axel (Instituto de Física - UNAM)

Presenter: Mr ALMARAZ AVIÑA, Erick Jonathan (Instituto de Física / UNAM)



28th Texas Symp … / Report of Contributions New connection between plasma c …


New connection between plasma conditions nearblack hole event horizons and outflow properties


Accreting black holes are responsible for producing the fastest, most powerful outflows of matterin the Universe. The formation process of powerful jets close to black holes is poorly understood,and the conditions leading to jet formation are currently hotly debated. In this talk I will presentrecent results that show empirical correlation between the properties of the plasma close to theblack hole and the particle acceleration properties within jets launched from the central regions ofaccreting stellar-mass and supermassive black holes. In these sources the emission of the plasmanear the black hole is characterized by a power law at X-ray energies during times when thejets are produced. We find that the photon index of this power law, which gives information onthe underlying particle distribution, correlates with the characteristic break frequency in the jetspectrum, which is dependent on magnetohydrodynamical processes in the outflow. The observedrange in break frequencies varies by five orders of magnitude, in sources that span nine orders ofmagnitude in black hole mass, revealing a similarity of jet properties over a large range of blackhole masses powering these jets. This correlation demonstrates that the internal properties of thejet rely most critically on the conditions of the plasma close to the black hole, rather than otherparameters such as the black hole mass or spin, and will provide a benchmark that should bereproduced by the jet formation models.

Primary author: KOLJONEN, Karri (New York University Abu Dhabi)

Co-authors: VAN DER HORST, Alexander (George Washington University); RUSSELL, Dave (NewYork University Abu Dhabi); BERNARDINI, Federico (New York University Abu Dhabi); MILLER-JONES,James (ICRAR/Curtin University); FERNANDEZ-ONTIVEROS, Juan (INAF/IAPS); CURRAN, Peter(ICRAR/Curtin University); CASELLA, Piergiorgio (INAF/Osservatorio Astronomico di Roma); GANDHI,Poshak (University of Southampton); SORIA, Roberto (ICRAR/Curtin University); MARKOFF, Sera(University of Amsterdam); RUSSELL, Thomas (ICRAR/Curtin University)

Presenter: KOLJONEN, Karri (New York University Abu Dhabi)



28th Texas Symp … / Report of Contributions Analysis update to the 2013 data fr …


Analysis update to the 2013 data from the LargeUnderground Xenon project


The Large Underground Xenon (LUX) project is a direct dark matter detection experiment usinga dual-phase Xenon time projection chamber. The analysis has been improved for the first 90 livedays of 2013 data while LUX collects another 300 live days of exposure. The enhancements includephoton counting of S1, total charge measurements of S2, more calibration data, new backgroundand signal models, and better position reconstruction. These upgrades allow for a lower energythreshold and better discrimination between signal and background events. The improved analysisstill gives a null result for both Spin Independent and Spin Dependent WIMPs, therefore limits onthe interaction cross sections were set. The resulting sensitivity to low mass WIMPs improvedby more than a factor x100 compared with the original analysis, and the sensitivity to high massWIMPs increased by about x1.5.

Collaboration

Large Ungerground Xenon Project

Primary author: TO, Wing (SLAC)

Presenter: TO, Wing (SLAC)



28th Texas Symp … / Report of Contributions First-order cosmological perturbat …


First-order cosmological perturbations engenderedby point-like masses: all scales covered


In the framework of the concordance cosmological model the first-order scalar and vector perturba-tions of the homogeneous background are derived without any supplementary approximations inaddition to the weak gravitational field limit. The sources of these perturbations (inhomogeneities)are presented in the discrete form of a system of separate point-like gravitating masses. The ob-tained expressions for the metric corrections are valid at all (sub-horizon and super-horizon) scalesand converge in all points except the locations of the sources, and their average values are zero(thus, first-order backreaction effects are absent). Both the Minkowski background limit and theNewtonian cosmological approximation are reached under certain well-defined conditions. Animportant feature of the velocity-independent part of the scalar perturbation is revealed: up toan additive constant it represents a sum of Yukawa potentials produced by inhomogeneities withthe same finite time-dependent Yukawa interaction range. The suggesting itself connection be-tween this range and the homogeneity scale is briefly discussed along with other possible physicalimplications.

Primary author: EINGORN, Maxim

Presenter: EINGORN, Maxim



28th Texas Symp … / Report of Contributions Quasi-scale invariant inflationary …


Quasi-scale invariant inflationary attractorsWednesday, December 16, 2015 5:35 PM (20 minutes)

Recently Kallosh, Linde, and collaborators have provided a unified description of single-field in-flation in terms of just one parameter α. These so-called α-attractors predict a spectral index n_sand a tensor-to-scalar ratio r, which are fully compatible with the latest Planck data. The onlycommon feature of all α-attractors is a non-canonical kinetic term with a pole, and a potentialanalytic around the pole.

Starting from the same Einstein frame with a non-canonical scalar kinetic energy, we explore thecase of non-analytic potentials and find that they all correspond to quasi-scale invariant gravita-tional models in the Jordan frame, characterised by a universal relation between r and ns that fitsthe observational data but is clearly distinct from the one of the α- attractors.

Since the breaking of the exact classical scale-invariance in the Jordan frame can be attributed toone-loop corrections, we desume that non-analytic potentials in the non-canonical Einstein frameare physically equivalent to an entire class of models in the Jordan frame, with scale-invariancesoftly broken by one-loop quantum corrections.

Collaboration

L. Vanzo; S. Zerbini; G. Cognola; G. Venturi

Primary author: RINALDI, Massimiliano (University of Trento)

Presenter: RINALDI, Massimiliano (University of Trento)



28th Texas Symp … / Report of Contributions Consistent massive graviton on an …


Consistent massive graviton on an arbitrarybackground


The only consistent linear theory for a massive spin-2 field on a flat space-time has been knownfor a long time as being the Fierz-Pauli theory. Its promotion to a non-linear theory, althoughessential, has long been thought impossible because of the appearance of the Boulware-Deser(BD) ghost. Recently, de Rham, Gabadadze and Tolley (dRGT) proposed a family of massive gravitytheories, free of the BD ghost. In this talk, I will present how to obtain, for the dRGT theories, thelinearized equations of motion for a massive graviton. More specifically I will focus on a particularsubset of these theories, for which it is possible to remove the need for a second reference metric,hence obtaining the equations of motion of a massive graviton moving in a single and arbitrarybackground metric. For this specific model I will derive the five covariant constraints necessaryto remove five degrees of freedom out of ten, among which the scalar constraint removes the BDghost. Then I will generalize the covariant constraint analysis to the whole dRGT theories.

Primary author: BERNARD, Laura (Université de Paris 6 - Pierre et Marie Curie)

Presenter: BERNARD, Laura (Université de Paris 6 - Pierre et Marie Curie)



28th Texas Symp … / Report of Contributions Formation of millisecond pulsars a …


Formation of millisecond pulsars and doubleneutron stars


Radio millisecond pulsars (MSPs) have been spun-up to very high rotation frequenciesvia accretion of mass and angular momentum from a companion star in a binary system.In this talk, I will review the formation of MSPs and discuss recent observationaland theoretical challenges in understanding their formation and evolution via thestandard recycling scenario. I will discuss MSP properties like spin periods, masses andorbital characteristics, and also briefly discuss new developments related to ourunderstanding of the formation of double neutron star systems.

Primary author: TAURIS, Thomas (Uni. Bonn)

Presenter: TAURIS, Thomas (Uni. Bonn)



28th Texas Symp … / Report of Contributions Constraints on Primordial Magnet …


Constraints on Primordial Magnetic Fields fromPlanck 2015


Primordial magnetic fields (PMF) may represent the “progenitors”of the fields we observe in large scale structures and theirstudy could open a new observational window on the early universe. TheCosmic Microwave Background, thanks to its different probes,represents one of the best laboratory to investigate and constrain thenature of PMF. I will present the Planck 2015 constraints on theamplitude and spectral index of a stochastic background of PMF derivedusing different methods.

Collaboration

D. Paoletti for the Planck Collaboration

Primary author: PAOLETTI, Daniela (INAF and INFN)

Presenter: PAOLETTI, Daniela (INAF and INFN)



28th Texas Symp … / Report of Contributions XIPE the X-ray Imaging Polarimet …


XIPE the X-ray Imaging Polarimetry ExplorerThursday, December 17, 2015 3:06 PM (19 minutes)

XIPE, the X-ray Imaging Polarimetry Explorer, is one of the three missions selected by ESA forstudy phase for down-selection of the fourth medium size mission. XIPE will measure the polariza-tion in hundreds of celestial sources of different classes. It will allow for answering, in a novel way,to questions related to the acceleration phenomena in PWNe, Supernovae and blazars, to the trans-port of radiation in plasma embedded in a strong magnetic field like in pulsating X-ray binaries, tothe scattering in a-spherical geometries, like in AGNs and in the molecular clouds located in thegalactic centre region and, finally, to fundamental physics. It will be operated as a conventionalX-ray observatory but providing polarimetry simultaneously to the usual imaging, temporal andspectral information. This is made possible by its unique payload configuration consisting of threeGas Pixel Detector at the focus of three large, albeit low-weight, X-ray telescopes and fitting in theVega launcher. In this talk I am reviewing the scientific capability of XIPE, the characteristics ofthe payload and the mission profile.

Collaboration

XIPE Collaboration

Primary author: Dr SOFFITTA, Paolo (IAPS/INAF)

Presenter: Dr SOFFITTA, Paolo (IAPS/INAF)



28th Texas Symp … / Report of Contributions Black hole mimickers


Black hole mimickersThursday, December 17, 2015 5:35 PM (20 minutes)

We show that a spherically symmetric gravitational collapse of a star can result in a bounce if theequation of state behaves with sufficient rigidity just before the formation of an event horizon. Therelativistic time dilation produced by the strong gravity makes the whole process to be undistin-guishable from a black hole on timescales shorter than the Hubble time for a distant observer. Wesolve the Misner-Sharp equations for stellar collapse with a suitable equation of state that reducesto a polytropic at low densities and mimicks an effective cosmological constant during the collapse,finally inverting the direction of the velocity field of the fluid. We also present some preliminaryresults of numerical simulations of these objects. We conclude that evolving gravitational systemsmight mimick, in this way, most of the properties attributed to static black holes.

Primary author: Mrs PEREZ, Daniela (Instituto Argentino de Radioastronomia)

Co-authors: Dr GOURGOULHON, Eric (Observatorie de Paris); Mr LOPEZ ARMENGOL, FedericoGaston (Instituto Argentino de Radioastronomia); Dr ROMERO, Gustavo Esteban (Instituto Argentinode Radioastronomia); Dr NOVAK, Jerome (Observatorie de Paris)

Presenter: Mrs PEREZ, Daniela (Instituto Argentino de Radioastronomia)



28th Texas Symp … / Report of Contributions Large Area X-ray Proportional Co …


Large Area X-ray Proportional Counter (LAXPC)instrument onboard ASTROSAT


ASTROSAT is India’s first science satellite dedicated to multiwavelength astronomy. It has fivescience payloads which will cover UV to hard X-ray in low earth orbit. LAXPC instrument is one ofthe major instruments (415 kg payload weight and above 100 electronic cards). This instrument isdesigned and developed at TIFR and all the three LAXPC flight units have successfully completedall space qualification tests as well as final calibration and have been handed over to ISRO forintegration with satellite during 2014. All science payloads have been integrated with satellite inMay 2015 and the integrated satellite tests were completed during June-July 2015 and now it isready to be launched on 28th September, 2015 from Sriharikota, India.We have developed GEANT4 simulations of LAXPC detectors and matched with actual calibrationdata. In orbit, LAXPC will provide largest effective area in the world for next 5-10 years in 3-80 keVenergy range. Large effective area, fine time resolution and moderate energy resolution will allowthe LAXPC instrument to probe certain properties of X-ray sources with unprecedented detail. Iwill describe the salient features of the LAXPC along with calibration results as well as some earlyresults from LAXPC instrument.

Primary author: Prof. YADAV, J S (Tata Institute of Fundamental Reaserch)

Presenter: Prof. YADAV, J S (Tata Institute of Fundamental Reaserch)



28th Texas Symp … / Report of Contributions The intriguing double torus-jet PW …


The intriguing double torus-jet PWN around PSRJ0855-4644


PSR J0855-4644 is a nearby, fast spinning, and energetic radio pulsar spatially coincident with therim of the supernova remnant RX J0852.0-4622 (aka Vela Jr). XMM Newton observations of the pul-sar region have shown an arcmin scale extended emission, the pulsar wind nebula (PWN), aroundthe X-ray counterpart of the pulsar. Here, we present results from the small scale structure of thenebula provided by a Chandra observation of this source. This observation has revealed an arcsecond scale compact PWN around the pulsar showing a possible double ‘torus+jet’ morphology.This makes it only the third source of its kind, and being an nearby object provides us with thegolden opportunity to investigate the physics of equatorial and polar outflows in PWNe. Model-ing the geometry of this source is also crucial to understand why no gamma-ray pulsations havebeen detected by the Fermi-LAT telescope for this high E_dot/d^2 pulsar. In order to constrain thepulsar spin inclination angle, we model the double torus morphology and then compare it withtheoretical phase-plots to understand this radio loud, gamma-ray quiet system.

Collaboration

Chandreyee Maitra, Fabio Acero and Christo Venter

Primary author: MAITRA, Chandreyee (CEA Saclay)

Co-authors: VENTER, Christo (North-West University Potchefstroom Campus); Dr ACERO, Fabio(CEA Saclay)

Presenter: MAITRA, Chandreyee (CEA Saclay)



28th Texas Symp … / Report of Contributions FACT: Monitoring TeV Blazars wi …


FACT: Monitoring TeV Blazars with SiliconPhotomultipliers


The First G-APD Cherenkov Telescope (FACT) has pioneered the use of solid state photosensors(G-APD/SiPM) in astroparticle physics. Data-taking started in October 2011, and the system hasoperated remotely for over three years. G-APDs have proven to be very reliable and have enabledFACT to produce the first Crab nebulae spectra from such an instrument and collect large unbiaseddata sets on extra-galactic blazars, including Mrk 501 and Mrk 421. These two objects are close-byand highly variable, providing us with an excellent opportunity to study this source class.

This presentation will describe the status of FACT and report the lessons learned regarding theusage of SiPM in Cherenkov telescopes. Contemporaneous correlations betweenFACT and measurements in other wavelengths will be shown, along with preliminary searches forquasi-periodic modulation. We will also present potential future extensions tothis technology that would enable the constant monitoring of these sources.

Collaboration

FACT Collaboration

Primary author: HUGHES, Gareth (ETH Zurich)

Presenter: HUGHES, Gareth (ETH Zurich)



28th Texas Symp … / Report of Contributions Covariant Perturbations of the …


Covariant Perturbations of the Scalar-TensorSchwarzschild Black Hole


In this talk I will review recent results regarding covariant, gauge-invariant perturbations to thescalar-tensor Schwarzschild black hole in the 1+1+2 formalism. I will discuss how we can introducea set of master functions based on the Weyl tensor in order to cleanly decouple the evolution oftensor modes from the scalar modes. Relations to 2+2 and Newman-Penrose formalism will bebriefly discussed.

Primary author: PRATTEN, Geraint (University of Sussex)

Presenter: PRATTEN, Geraint (University of Sussex)



28th Texas Symp … / Report of Contributions Multi-wavelength observations on …


Multi-wavelength observations on the gamma-rayperiodic blazar PG1553+113


PG 1553+113 is a blazar with an uncertain redshift detected at very high energies (VHE; E > 100GeV) both during high and quiescent flux states. The Fermi/LAT collaborationrecently reported the detection of a ~2-year modulation of the integral flux emitted in both opti-cal and high-energy (HE) gamma rays(Stamerra et al. at this conference). Interestingly, one ofthe physical scenarios that can account for such variability pattern is the presence of a supermas-sive black hole binary in the nucleus of PG 1553+113. The MAGIC telescopes have observed PG1553+113 at VHE since 2005. An intense multi-wavelength campaign aimed at unbiased monitor-ing of the source activity, from radio to VHE gamma rays, started in 2015. Here we will show themultiwavelength data going back almost a decade, from radio to VHE, along with the results fromthe ongoing observations.

Collaboration

MAGIC Collaboration

Primary author: HUGHES, Gareth (ETH Zurich)

Co-authors: Dr SANDRINELLI, Angela (Università degli Studi dell’Insubria); STAMERRA, Anto-nio (INAF-OATo / SNS-Pisa); Dr FERRIGNO, Carlo (ISDC data center for astrophysics); GASPARRINI,Dario (ASDC/ INFN Perugia); LINDFORS, Elina (University of Turku); PRANDINI, Elisa (Universityof Geneva); LONGO, Francesco; BECERRA GONZALEZ, Josefa (NASA GSFC); Dr NIEVAS, Miguel(Complutense University of Madrid); Dr DA VELA, Paolo (INFN Pisa); DESIANTE, Rachele (Univer-sità di Udine and INFN); CUTINI, Sara (ASI Science Data Center - INFN); PAIANO, Simone (Univ. +INFN); CIPRINI, Stefano (INFN & University Perugia); COVINO, Stefano (INAF / Brera); BARRES,Ulisses (Centro Brasileiro de Pesquisas Físicas)

Presenter: HUGHES, Gareth (ETH Zurich)



28th Texas Symp … / Report of Contributions Thermal emission in GRB 101219B


Thermal emission in GRB 101219BMonday, December 14, 2015 2:00 PM (21 minutes)

In recent years there has been growing evidence that emission from the photosphere of the jetcontributes to the prompt emission in many GRBs. The photospheric emission is usually seento coexist with a dominant non-thermal component. In this talk I will present an analysis ofGRB 101219B, the second burst observed by Fermi GBM that is well described by pure blackbodyemission. This burst also has a previously reported detection of a blackbody component at soft X-ray energies in the early afterglow observed by Swift. There is no smooth connection between thetwo blackbody components, ruling out the scenario that the late emission is due to high-latitudeeffects. The observed properties of the blackbody emission, together with the known redshift andour estimate of the radiative efficiency, makes it possible to calculate the properties of the jet withinthe standard fireball model. This yields an initial Lorentz factor of ~140 and a nozzle radius of ~3×107 cm. The latter value is close to the event horizon for a stellar-mass black hole and suggeststhat the jet has a relatively unobstructed path through the star.

Primary author: Dr LARSSON, Josefin (KTH Royal Institute of Technology)

Presenter: Dr LARSSON, Josefin (KTH Royal Institute of Technology)



28th Texas Symp … / Report of Contributions Non-thermal particle acceleration i …


Non-thermal particle acceleration in astrophysicalshear flows.


The non-thermal radiation seen from astrophysical objects bearswitness to the presence of energetic charged particles that haveexperienced efficient acceleration within these sources.

Shear flows are naturally expected in many of these environments.Combined with new observational results in the radio and high energygamma-ray domain and with progress in our understanding of turbulencemodelling, this has given fresh impetus to shear accelerationand emission scenarios.

Here we will review key results concerning the stochastic accelerationof energetic electrons and protons in gradual shear flows, highlightexpected spectral characteristics and report on recent applications inthe context of expanding relativistic outflows.

Primary author: RIEGER, Frank (MPIK and Univ. of Heidelberg)

Presenter: RIEGER, Frank (MPIK and Univ. of Heidelberg)



28th Texas Symp … / Report of Contributions Status of the Advanced Virgo project


Status of the Advanced Virgo projectTuesday, December 15, 2015 11:55 AM (35 minutes)

The european detector Advanced Virgo is ending the installation phase and the plan is to runduring 2016 joining the LIGO detectors installed in USA. Its improved sensitivity will increase thedetection probability of GW events.In this talk we summarize the scientific outcome of the old network of advanced detectors inthe past configuration. Then, we emphasize the potentialities of the new network in the contextof the multimessenger astronomy. which will combine the GW information with those of theelectromagnetic and neutrino signals likely emitted during the same astrophysical process.

Collaboration

Fulvio Ricci on behalf of the Virgo collaboration

Primary author: Prof. RICCI, Fulvio (University of Rome La Sapienza and INFN Sez. Roma)

Presenter: Prof. RICCI, Fulvio (University of Rome La Sapienza and INFN Sez. Roma)



28th Texas Symp … / Report of Contributions Short gamma-ray bursts from bina …


Short gamma-ray bursts from binary neutron starmergers: the time-reversal scenario


Leading models relate short gamma-ray bursts (SGRBs) to a relativistic jet launched by the blackhole (BH)-accretion torus system that can be formed in a binary neutron star (BNS) or a NS-BHbinary merger. However, recent observations by Swift have revealed a large fraction of SGRBevents accompanied by X-ray afterglows with durations ∼ 102 − 105 s, suggesting continuousenergy injection from a long-lived central engine that is incompatible with the short (< 1 s) ac-cretion timescale of a BH-torus system. The formation of a supramassive NS (SMNS), resistingthe collapse on much longer spin-down timescales, can explain these X-ray afterglows as poweredby the magnetic spin-down of the star, but leaves serious doubts on whether a relativistic jet canbe launched at merger. Here we present a novel “time-reversal” scenario that can solve this di-chotomy. In this scenario, the SGRB is produced after the eventual collapse of the SMNS to a BH,but observed before part of the long-lasting X-ray signal powered by magnetic spin-down.

Primary author: Dr CIOLFI, Riccardo (University of Trento and INFN-TIFPA)

Co-author: Mr SIEGEL, Daniel (Max Planck Institute for Gravitational Physics (Albert EinsteinInstitute))

Presenter: Dr CIOLFI, Riccardo (University of Trento and INFN-TIFPA)

28th Texas Symp … / Report of Contributions Electromagnetic emission from …


Electromagnetic emission from long-lived binaryneutron star merger remnants


Recent observations indicate that in a large fraction of binaryneutron star (BNS) mergers a long-lived neutron star (NS) may beformed rather than a black hole. Unambiguous electromagnetic (EM) signatures ofsuch a scenario would strongly impact our knowledge onhow short gamma-ray bursts (SGRBs) and their afterglow radiation aregenerated. Furthermore, such EM signals wouldhave profound implications for multimessenger astronomy with jointEM and gravitational-wave (GW) observations of BNS mergers, which willsoon become realitywith the ground-based advanced LIGO/Virgo GW detector network startingits first science run this year. Here we present a model to bridge the gap between numericalsimulations of the merger process and the relevant timescales forthe afterglows, assuming that the merger results in a long-lived NS. It provides a self-consistentevolution of the post-merger system and its EM emission starting from an early baryonic windphase and resulting in a final pulsar wind nebula that is confined by the previously ejected material.We present lightcurves and spectra and discuss these results in the context of SGRBs, their X-rayafterglows, and multimessenger astronomy.

Primary author: Mr SIEGEL, Daniel (Max Planck Institute for Gravitational Physics (Albert EinsteinInstitute))

Co-author: Dr CIOLFI, Riccardo (University of Trento and INFN-TIFPA)

Presenter: Mr SIEGEL, Daniel (Max Planck Institute for Gravitational Physics (Albert Einstein Insti-tute))



28th Texas Symp … / Report of Contributions Proposed Laboratory Simulation o …


Proposed Laboratory Simulation of Galactic PositronIn-Flight Annihilation in Atomic Hydrogen


Positron annihilation at 511 keV coming from the direction of the Galactic Center could be occur-ring in a variety of different ways. One channel, in-flignt annihilation, occurs by charge exchangeapproximately below 100 eV as positrons slow by inelastic collisions from keV energies. The char-acteristic Doppler broadened line width and shape is of interest in comparing to galactic gammaray data from the SPI/Integral telescope.[1] Laboratory experiments in the 1980’s simulated an-nihilation in-flignt in molecular hydrogen and helium.[2] However, the laboratory simulation inatomic hydrogen, proposed here, has only been done with Monte Carlo methods to date. Thereis a discrepancy of a factor of two in the present laboratory measurements of the positron-atomichydrogen impact ionization cross section, which affects the predicted in-flight annihilation line-width appreciably. Thus, laboratory measurements of in-flight positron annihilation in atomichydrogen will be useful at this time to accurately predict this possible component of the Dopplerbroadened 511 keV annihilation radiation from the Galactic Center.[1.] E. Churazov, S. Sazonov, S. Tsygankov, R. Sunyaev, D. Varshalovich, 2010, Mon. Not. R. As-tron. Soc. 411, 1727.[2.] B. L. Brown, M. Leventhal, A.P. Mills, & D.A. Gidley, 1984, Phys. Rev. Lett. 53, 2347.

Collaboration

ETH-MARQUETTE

Primary author: Prof. BROWN, Benjamin (Marquette University)

Co-author: CRIVELLI, Paolo (Eidgenoessische Tech. Hochschule Zuerich (CH))

Presenter: Prof. BROWN, Benjamin (Marquette University)



28th Texas Symp … / Report of Contributions TSPT: Time-Sliced Perturbation T …


TSPT: Time-Sliced Perturbation Theory for LargeScale Structure


I will present a new perturbative approach to the description of cosmological structures in themildly non-linear regime relevant at the distance scales from 10 to 100 Mpc. In this frameworkequal-time correlation functions of cosmological perturbations are calculated using an ensemblewith time-dependent statistical weight. The scheme is free from unphysical infrared divergenciesplaguing the traditional approaches and allows a systematic resummation of large infrared contri-butions to all orders of the perturbation theory. This greatly improves the description of the den-sity power spectrum in the region of baryon acoustic oscillations. I will mention future directions,which include infrared resumption of higher-point correlation functions and renormalisation ofthe contributions coming from short-wavelength modes.

Primary author: SIBIRYAKOV, Sergey (CERN & EPFL & INR RAS)

Presenter: SIBIRYAKOV, Sergey (CERN & EPFL & INR RAS)



28th Texas Symp … / Report of Contributions Relativistic effects in large-scale st …


Relativistic effects in large-scale structure surveysMonday, December 14, 2015 10:10 AM (35 minutes)

The distribution of galaxies provides a powerful way to probe the properties of our universe. Inorder to exploit this observable properly it is necessary to understand what we are really measuringwhen we look at the large-scale structure. Since our universe is not completely homogeneous andisotropic, we only see a distorted picture of our sky. In this talk, I will discuss the various relativisticeffects that distort our observations. I will show that even though these effects complicate theinterpretation of galaxy surveys, they are very useful since they contain information about thetheory of gravity and can therefore be regarded as a new opportunity for future surveys.

Primary author: BONVIN, Camille (CERN)

Presenter: BONVIN, Camille (CERN)



28th Texas Symp … / Report of Contributions Unveiling the self-coupling of dark …


Unveiling the self-coupling of dark matter withgalaxy clusters


Recent studies into the dynamics of galaxy clusters and galaxy cluster members have revealed po-tential signatures of self-interacting dark matter. In this talk I will discuss the current evidencethat supports this hypothesis and the observational signals that self-interacting dark matter maymanifest itself as. I will finish by presenting current work and observations from the worlds besttelescopes that continue to probe this potentially revealing property of the Universe’s most mys-terious matter.

Primary author: HARVEY, David Richard (EPFL - EPF Lausanne)

Presenter: HARVEY, David Richard (EPFL - EPF Lausanne)



28th Texas Symp … / Report of Contributions Broadband study of X-Per using S …


Broadband study of X-Per using Suzaku observationsMonday, December 14, 2015 6:05 PM (15 minutes)

We present detailed broadband timing and spectral analysis of the persistent, low luminosity andslowly spinning pulsar ‘X-per’ using a Suzaku observation of the source. The spectrum is unusuallyhard with pulsations detected up to 70 keV. The spectrum also hosts several interesting featureslike evidence of a cyclotron line at 30 keV, and presence of a soft-excess below 2 keV. Consider-ing these, the broadband Suzaku observation is ideal to study the energy dependence of the pulseprofiles, and critically compare the different spectral models of accretion powered pulsars appli-cable to the source. The hardness ratio varies by more than a factor of two during the duration ofthe observation, and the change in spectral parameters are mapped by performing time resolvedspectroscopy. The results are compared with other persistent Be accreting systems.

Collaboration

Chandreyee Maitra, Pragati Pradhan, Biswajit Paul and Harsha Raichur

Primary author: MAITRA, Chandreyee (CEA Saclay)

Co-authors: Prof. PAUL, Biswajit (Raman Research Institute, India); Dr RAICHUR, Harsha (NordicInstitute for Theoretical Physics); Ms PRADHAN, Pragati (North Bengal University, India)

Presenter: MAITRA, Chandreyee (CEA Saclay)



28th Texas Symp … / Report of Contributions One-dimensional models of cosmo …


One-dimensional models of cosmologicalperturbations: direct integration in the Fourier space


We propose a numerical approach to study the inhomogeneity growth in the Universe filled witha pressureless matter. The hydrodynamical equations for perturbations of the isotropic uniformcosmological background (non-relativistic stage) in the comoving frame are treated taking into ac-count all nonlinear terms. The periodic boundary conditions are imposed. The problem is reducedto ordinary differential equations for an infinite chain of Fourier coefficients for hydrodynamicalvariables. We perform a numerical integration of these equations for randomly generated initialconditions (with proper truncation of the coefficients). This procedure is repeated for a numberof representations of the ensemble of initial conditions to obtain a power spectrum of the densitycontrast. We test the method in two problems. (i) We derived an exact implicit solution whichdescribes a one-dimensional collapse of plane gravitating shells. This is used to check the numer-ical solution for the Fourier coefficients and for the power spectrum. (ii) In case of the standardthree-dimensional hydrodynamical equations but with one-dimensional (plane) initial conditionswe proceed only numerically to derive first coefficients of the power spectrum. The results areused to study a nonlinear interaction of different Fourier modes. We estimate a realizability of thismethod as an alternative to the cosmological N-body simulations in case of a mildly non-linearsituation.

Primary authors: Prof. ZHDANOV, Valery (Astronomical Observatory of Taras Shevchenko Na-tional University of Kyiv, Ukraine); SLIUSAR, Vitalii (Astronomical Observatory of Taras ShevchenkoNational University of Kyiv, Ukraine)

Presenter: SLIUSAR, Vitalii (Astronomical Observatory of Taras Shevchenko National University ofKyiv, Ukraine)



28th Texas Symp … / Report of Contributions Gravitational microlensing as a pr …


Gravitational microlensing as a probe for darkmatterThursday, December 17, 2015 4:55 PM (20 minutes)

We study effects due to a possible presence of putative dark matter mini-halos (DM clumps) inthe light curves of source images of the extragalactic gravitational lens systems. The extendedclumps are described by means of a simplified model of the lens mapping. Every microlens consistsof a central point mass surrounded by a concentric extended mini-halo; this is characterized bythe ratio q of the extended mass to the point one, the typical size R and the total mass M. Weconsider the microlensing of a remote source by a stochastic system of such microlenses. Thespatial distribution of microlenses is assumed to be uniform; the distribution of M have been chosenaccording to the Salpeter law for different fixed values of R and q. To have a significant effectwe have chosen the size R to be comparable with the radius of the Einstein-Chwolson ring of amicrolens. The motion of a source with respect to the microlenses induces a dependence of theamplification of the source image upon the time (amplification curve). We obtain an ensembleof the amplification curves for a number of realizations of the microlensing field. This is usedto derive autocorrelation functions of the light curves by means of an averaging procedure. Thederivation is fulfilled for different values of the microlensing optical depth and the external shear,as well as for different values of q and R.

Primary authors: Dr ALEXANDROV, Alexander (Astronomical Observatory of Taras ShevchenkoNational University of Kyiv, Ukraine); Prof. ZHDANOV, Valery (Astronomical Observatory of TarasShevchenko National University of Kyiv, Ukraine); SLIUSAR, Vitalii (Astronomical Observatory of TarasShevchenko National University of Kyiv, Ukraine)

Presenter: SLIUSAR, Vitalii (Astronomical Observatory of Taras Shevchenko National University ofKyiv, Ukraine)



28th Texas Symp … / Report of Contributions Interacting pulsar winds in X-ray a …


Interacting pulsar winds in X-ray and gamma-raybinaries


The presence of a relativistic pulsar wind has been established in several X-ray binaries. Theinteraction of the pulsar wind with the stellar companion, stellar wind, or accretion disk can leadto peculiar signatures, most prominently the emission of high-energy gamma-rays. I will describeour efforts to model this interaction in order to translate gamma-ray observations into a betterunderstanding of relativistic magnetized outflows.

Primary author: DUBUS, Guillaume (IPAG CNRS/Université Grenoble Alpes)

Presenter: DUBUS, Guillaume (IPAG CNRS/Université Grenoble Alpes)



28th Texas Symp … / Report of Contributions Study of GRB light curve decay in …


Study of GRB light curve decay indices in theafterglow phase


In this work we study the distribution of temporal power-law decay indices, α, in the Gamma RayBurst (GRB) afterglowphase,fitted for a sample of 164 long GRBs with known redshifts using a power-law form. These indicesare compared to the values of characteristic afterglowluminosity,La, the time, T ∗

a , and the analogous decay index, αW , derived with global light curve fitting usingthe Willingale et al. (2007) model.This model fitting yields similar distributions of αW to the fitted α, but for several bursts differencebetweenthese indicescan be significant. Analysis of the (α, La) distribution reveals a weak correlation of these quanti-ties. However, wediscovereda significant regular trend when studying distribution of GRB α values at the La, vs. T ∗

a (LT) plane,with a differences of the α parameters below and above the fitted LT correlation line (Dainotti etal. 2008).Study of the presented systematic trend may allow one for constraining the physical models forGRBs. A proposed toy model accountingfor this systematics applied to the analyzed GRB distribution results in increasing the LT correla-tion coefficient.

Collaboration

Del Vecchio Roberta, Dainotti Maria Giovanna, Ostrowski Michał

Primary author: Mrs DEL VECCHIO, Roberta (Astronomical Observatory of the Jagiellonian Uni-versity)

Co-authors: Dr DAINOTTI, Maria Giovanna (Stanford University); Prof. OSTROWSKI, Michał(Astronomical Observatory Jagiellonian University)

Presenter: Mrs DEL VECCHIO, Roberta (Astronomical Observatory of the Jagiellonian Univer-sity)



28th Texas Symp … / Report of Contributions Neutrinos beyond the linear regim …


Neutrinos beyond the linear regime: a newtheoretical approach


There is now no doubt that neutrinos are massive particles fully involved in the nonlinear growth ofthe large-scale structure of the universe. A problem is that their nonlinear behavior is particularlydifficult to describe by theoretical models. In my talk, I will present a new method allowing todeal with massive neutrinos beyond the linear regime. The key idea is to describe neutrinos as acollection of flows instead of considering them as a single multi-flow fluid. In this framework, novelocity dispersion has to be taken into account and the time evolution of neutrinos can be encodedin fluid equations similar to the ones describing cold dark matter. Hopefully, this approach is afurther step towards a computation of the nonlinear matter power spectrum in the presence ofmassive neutrinos.

Primary author: DUPUY, Hélène

Co-author: Dr BERNARDEAU, Francis (Institut d’astrophysique de Paris)

Presenter: DUPUY, Hélène



28th Texas Symp … / Report of Contributions Saturation of the f-mode instability …


Saturation of the f-mode instability in neutron starsThursday, December 17, 2015 2:40 PM (20 minutes)

Due to the Chandrasekhar-Friedman-Schutz (CFS) instability, the f-mode (fundamental oscillation)in a newborn neutron star is driven unstable by the emission of gravitational waves. This staris usually the result of a core-collapse supernova explosion, but may also be the aftermath ofa binary neutron star merger, where a rapidly rotating, supramassive configuration is formed,before its collapse to a black hole. The instability is halted by non-linear coupling to other modesof the star, which drain energy and saturate it. Depending on the saturation point, the generatedgravitational wave signal could be detected by the next generation gravitational wave detectorsand, thus, provide useful information about the neutron star equation of state.

Primary author: PNIGOURAS, Pantelis

Presenter: PNIGOURAS, Pantelis



28th Texas Symp … / Report of Contributions Initial conditions for simulations o …


Initial conditions for simulations of arbitrarymodified gravity, beyond quasi-static

approximationsWednesday, December 16, 2015 3:04 PM (21 minutes)

I will present a novel description for setting initial particle displacements and field values underarbitrary metric theories of gravity, for perfect and imperfect fluids with arbitrary characteristics.We extend the Zel’dovich Approximation to nontrivial theories of gravity, and show how scale de-pendence implies curved particle paths, even in the entirely linear regime of perturbations. Initialconditions set at high redshifts are affected at the level of up to 5% at Mpc scales, which exemplifiesthe importance of going beyond ΛCDM initial conditions for modifications of gravity outside ofthe quasi-static approximation. Our description paves the way for simulations and mock galaxycatalogs under theories of gravity beyond the standard model, crucial for progress towards preci-sion tests of gravity and cosmology.

Primary author: VALKENBURG, Wessel (Leiden University)

Presenter: VALKENBURG, Wessel (Leiden University)



28th Texas Symp … / Report of Contributions The MICROSCOPE mission ready t …


The MICROSCOPE mission ready to test theEquivalence Principle in space


MICROSCOPE is a French Space Agency scheduled for launch in 2016, that aims to test the WeakEquivalence Principle in space: one century after the publication of Einstein’s General Relativity,it could allow us to reveal a breach in the theory. Thanks to its cutting-edge-technology inertialsensors, it will allow us to measure the Eotvos parameter down to 10−15, two orders of magnitudebetter than the best current constraints. In this talk, I will motivate the science behind MICRO-SCOPE and present the mission. I will then summarize its status, with an emphasis on how wewill tackle the data analysis challenges.

Primary author: BERGE, Joel (ONERA)

Presenter: BERGE, Joel (ONERA)



28th Texas Symp … / Report of Contributions Jets and winds from super-critical …


Jets and winds from super-critical accreting blackholes


Determining the power output and efficiency of accreting black holes is a fundamental astrophys-ical problem:we want to know the relation between mass accretion rate, radiative output (photons) and me-chanical output(kinetic energy of jets and winds). We focus in particular on off-nuclear black holes that are ac-cretingfrom a donor star at a rate near or above the critical Eddington limit. Many of them appear as“ultraluminousX-ray sources”, evidence of their high radiative output. But how much additional power is carriedby winds and jets?To answer this question, we studied a sample of powerful black holes associated with large bubblesof shock-ionizedand/or photo-ionized gas. We used the bubbles as calorimeters to measure the power injected bythe black holeinto its surroundings. We find that black holes at super-Eddington accretion rates can have a me-chanical powercomparable to their radiative luminosity. Our study provides empirical constraints for theoreticalmodelsof super-Eddington accretion, and for models of black hole feedback in the early universe.

Primary author: Dr SORIA, Roberto (ICRAR-Curtin University)

Co-authors: Dr MOTCH, Christian (University of Strasbourg); Dr GRISE’, Fabien (University ofStrasbourg); Dr MILLER-JONES, James (ICRAR-Curtin University); Prof. PAKULL, Manfred (Univer-sity of Strasbourg)

Presenter: Dr SORIA, Roberto (ICRAR-Curtin University)



28th Texas Symp … / Report of Contributions Confronting anisotropic cosmolog …


Confronting anisotropic cosmological models withreal-time cosmology


A repetition of the same high-resolution and large-volume observation, after ten or more years,gives access to the fourth dimension in observational cosmology, perpendicular to the light-cone.I discuss how various toy models can be distinguished by decomposing the long-time-differencemaps into multipole vectors. A next-generation GAIA-like satellite with ten times GAIA’s resolu-tion, should be able to distinguish rotation from anisotropic expansion.

Primary author: VALKENBURG, Wessel (Leiden University)

Presenter: VALKENBURG, Wessel (Leiden University)



28th Texas Symp … / Report of Contributions Relativistic Astrophysics with ALMA


Relativistic Astrophysics with ALMAThursday, December 17, 2015 4:55 PM (20 minutes)

The Atacama Large Millimetre/Sub-millimetre Array, ALMA, is the leading instrument for obser-vations in the frequency range from 35 to 950 GHz. It is an aperture-synthesis array consistingof 66 antennas of 12 and 7m diameter equipped with sensitive receivers located at 5000m altitudeon the Chajnantor Plateau in Northern Chile. ALMA is just entering its third observing cycle andis producing transformational science in many areas of astronomy. I will review ALMA’s currentand potential contributions to relativistic astrophysics, including the estimation of magnetic fieldsin accretion disks and the derivation of physical parameters in jets. ALMA is currently being up-graded to act as a phased array, in which the signals from 50 of its antennas are combined to givethe equivalent of a single dish with a diameter of 84m. This will allow it to be used as an elementof a very sensitive global Very Long Baseline array with a resolution of 10’s of microarcsec at 230and 345 GHz. Imaging of the event horizon shadows around the black holes in the Galactic Centreand M87 will become possible for the first time, leading to stringent tests of General Relativity.The jet launching zone in nearby radio galaxies such as M87 and Centaurus A will be resolved andimaged. Phased ALMA alone will enable complementary tests of General Relativity by finding andtiming millisecond pulsars orbiting the Galactic Centre black hole.

Primary author: LAING, Robert (ESO)

Presenter: LAING, Robert (ESO)



28th Texas Symp … / Report of Contributions Signs of Blandford & Znajek mech …


Signs of Blandford & Znajek mechanism in GRBafterglow lightcurves.


According to Blandford & Znajek (1977), the spin energy of a rotating black hole can be extractedelectromagnetically, should the hole be endowed with a magnetic field supported by electric cur-rents in a surrounding disk. We argue that this can be the case for the central engines of GRBsand we show that the duration of the burst depends on the magnetic flux accumulated on theevent horizon of the black hole. We show that in several GRBs the theoretical curve of black holespin down follows closely the energy flux (lightcurve). As a result we estimate the magnetic fieldstrength at the vicinity of the black hole. Thus, we conclude that these GRBs have outflows withordered magnetic fields and we estimate the field strength throughout the jet.

Primary author: NATHANAIL, Antonio

Presenter: NATHANAIL, Antonio



28th Texas Symp … / Report of Contributions Relativistic Speeds and Transverse …


Relativistic Speeds and Transverse Velocity Structureon 50 kpc Scales in NGC6251


We present new, deep, high-resolution images of the iconic jets in the nearby radio galaxy NGC6251 made with the Karl G. Jansky VLA, resolving the faint counter-jet in width for the first time.We model the jet velocity field using the method of Laing & Bridle (2002, 2014). We assume thatthe jets are intrinsically symmetrical, axisymmetric, stationary flows and fit to images of linearpolarization as well as total intensity. We show that the jets have transverse velocity structure, witha high Lorentz factor spine surrounded by a mildly relativistic shear layer. The jets in NGC6251,unlike those we have studied previously, maintain high speeds out to at least 50 kpc from thenucleus rather than decelerating rapidly. The dominant magnetic field component in the jet islongitudinal close to the nucleus and toroidal at large distances.

Primary author: LAING, Robert (ESO)

Co-authors: Dr BRIDLE, Alan (NRAO); Dr PERLEY, Richard (NRAO)

Presenter: LAING, Robert (ESO)



28th Texas Symp … / Report of Contributions The universal model of cosmic ray …


The universal model of cosmic ray productionThursday, December 17, 2015 4:35 PM (20 minutes)

It seems to be a striking coincidence that all putative cosmic raysources which are dynamically able to fill the universe with the observedextragalactic cosmic ray density can produce the same maximum confinementenergy, eBR ~ 10^20 eV, while being spread in scale R over 10 orders ofmagnitude - the most impressive representation of this coincidence is the famousHillas plot, in which all “interesting” sources of extragalactic cosmic raysfall on one line. We present here a potential explanation for this, by assumingthat cosmic ray production is a byproduct of the generation of turbulence duringthe gravitational contraction of the Universe, i.e. structure formation. Themodel naturally explains why the maximum confinement energy is scale invariant,while reproducing BOTH the value of the maximum energy (~10^20 eV) and theoverall extragalactic production rate, ~10^47 erg / Mpc^3 / year for aproduction spectral index of E^-2.3, from known cosmological parameters plus ONEfree parameter, which is the fraction of gravitational energy transformed intoturbulence and found to be close to its canonical expectation value. While thegeneric approach presented here can certainly not compete with detailed modelingof specific cosmic ray sources, it predicts the fractional energeticcontribution of sources acting at different scales, and can thus serve as atheoretical prior for extragalactic cosmic ray production in Bayesian modelingof the large scale Galactic Magnetic Field from UHECR arrival directions.

Primary author: RACHEN, Jörg Paul (IMAPP / Radboud University Nijmegen)

Presenter: RACHEN, Jörg Paul (IMAPP / Radboud University Nijmegen)



28th Texas Symp … / Report of Contributions Does the obscured AGN fraction r …


Does the obscured AGN fraction really depend onluminosity?


We have utilized a local AGN sample from the INTEGRAL all-sky hard X-ray survey to investigateif the well-known declining trend of the fraction of obscured AGN with increasing luminosity ismostly an intrinsic or selection effect. We show that in addition to negative bias, due to absorptionin the torus, in finding obscured AGN, there is positive bias in finding unobscured AGN, due toCompton reflection in the torus. These biases lead to a decreasing observed fraction of obscuredAGN with increasing luminosity even if this fraction has no intrinsic luminosity dependence, thiseffect being stronger if there is intrinsic collimation of hard X-ray emission along the axis ofthe torus. We conclude that if the central AGN source is isotropic, the intrinsic obscured AGNfraction does decrease with increasing luminosity, although this fraction is higher than thoughtbefore: >85% at L<10^42.5 erg/s and <60% at L>10^44 erg/s (17-60 keV), which implies that thetorus half-opening angle is <30 deg and >45 deg, respectively. If, however, the emission from thecentral SMBH is moderately collimated, the intrinsic obscured AGN fraction is consistent with aluminosity-independent torus half-opening angle of ~30 deg.

MNRAS (in press), arXiv:1509.01259

Primary author: Dr SAZONOV, Sergey (Space Research Institute, Moscow, Russia)

Co-authors: Dr CHURAZOV, Eugene (IKI, Moscow; MPA, Garching); Dr KRIVONOS, Roman (IKI,Moscow)

Presenter: Dr SAZONOV, Sergey (Space Research Institute, Moscow, Russia)

28th Texas Symp … / Report of Contributions The variation of the fine-structure …


The variation of the fine-structure constant fromdisformal couplings


We study a theory in which the electromagnetic field is disformally coupled to a scalar field, in addi-tion to a usual non–minimal electromagnetic coupling. We show that disformal couplings modifythe expression for the fine–structure constant, α. As a result, the theory we consider can explainthe non–zero reported variation in the evolution of α by purely considering disformal couplings.We also find that if matter and photons are coupled in the same way to the scalar field, disformalcouplings itself do not lead to a variation of the fine–structure constant. A number of scenariosare discussed consistent with astrophysical, geochemical, laboratory and the cosmic microwavebackground radiation constraints on the cosmic evolution of α. We also use cosmological data, in-cluding type Ia supernova data for which we present an effective dark energy equation of state. Wefind that the Oklo bound in particular will put strong constraints on the model parameters. Fromour numerical results, we find that the introduction of a non–minimal electromagnetic couplingenhances the cosmological variation in α. Better constrained data is expected to be reported byALMA and with the forthcoming generation of high–resolution ultra–stable spectrographs suchas PEPSI, ESPRESSO, and ELT–HIRES. Furthermore, an expected increase in the sensitivity ofmolecular and nuclear clocks will put a more stringent constraint on the theory.

Primary authors: Prof. VAN DE BRUCK, Carsten (Consortium for Fundamental Physics, School ofMathematics and Statistics, University of Sheffield); Mr MIFSUD, Jurgen (Consortium for FundamentalPhysics, School of Mathematics and Statistics, University of Sheffield); Prof. NUNES, Nelson (Institutode Astrofisica e Ciencias do Espaco, Faculdade de Ciencias da Universidade de Lisboa)

Presenter: Mr MIFSUD, Jurgen (Consortium for Fundamental Physics, School of Mathematics andStatistics, University of Sheffield)



28th Texas Symp … / Report of Contributions CMB spectral distortions: energy r …


CMB spectral distortions: energy release versusphoton injection


CMB spectral distortions caused by energy release in the early Universe create broad distortionsthat are usually described as superposition of mu-, y- and r-type distortions. These signals willallow us to gain new insights into the pre-recombination Universe, telling us about early-universeand particle physics. There is, however, another way to create distortions: by photon injection. Oneexample is related to the hydrogen and helium recombination radiation emitted around z~1000,however, similarly decaying and annihilating particle scenarios or super-conducting strings shouldlead to copious photon production. The types of distortions that are created by photon injectionshow a much richer phenomenology than the classical mu and y distortions, as I will illustrate inmy talk. This may provide additional ways of distinguishing different energy release mechanisms.

Primary author: CHLUBA, Jens (Institute of Astronomy)

Presenter: CHLUBA, Jens (Institute of Astronomy)



28th Texas Symp … / Report of Contributions Coeval observations of a complete …


Coeval observations of a complete sample offlat-spectrum blazars with Effelsberg, IRAM 30m,

and PlanckWednesday, December 16, 2015 3:42 PM (3 minutes)

We present time-resolved broad-band spectra of a completesample of blazars, selected by showing flat radio spectra up to 143GHz, taken from observations with Planck, the Effelsberg 100mtelescope, and the IRAM 30m telescope. Dedicated Effelsbergobservations have been focused on times within two months aroundPlanck single survey scans of each source, with a cadence of 2-4 weeksduring the 4th and 5th Planck survey. The data are complemented withflux measurements from the F-GAMMA program (Fuhrmann et. al, 2007,AIPC 921, 249; Fuhrmann et al., 2014, MNRAS 441, 1899), and from otherEffelsberg and IRAM monitoring programs, as far as available. Planckdata are extracted employing methods used in the blind search forvariable sky signals, which allow to estimate snap-shot source fluxesdown to pointing period (i.e. hour scale) time resolution (Rachen etal., Proc IAU GA 2015). The program thus covers 15 frequencies between2.4 to 857 GHz and is sensitive to variability time scales from hoursover weeks up to one year, which is unprecedented in the history ofblazar monitoring.

Primary authors: RACHEN, Jörg Paul (IMAPP / Radboud University Nijmegen); FUHRMANN,Lars (Max-Planck-Institute for Radioastronomy)

Co-authors: SIEVERS, Albrecht (IRAM / Spain); ZENSUS, Anton (MPI für Radioastronomie); KEI-HANAN, Elina (University of Helsinki); ANGELAKIS, Emmanouil (MPI für Radioastronomie); UN-GERECHTS, Hans (IRAM / Spain); NESTORAS, Ioannis (MPI für Radioastronomie); REINECKE, Martin(MPI für Astrophysik); KRICHBAUM, Thomas (MPI für Radioastronomie)

Presenter: RACHEN, Jörg Paul (IMAPP / Radboud University Nijmegen)



28th Texas Symp … / Report of Contributions Searches for ultra-high energy neu …


Searches for ultra-high energy neutrinos andphotons with the Pierre Auger Observatory


Ultra-high energy (UHE) neutrinos and photons travel undeflected through cosmic magnetic fields,and point directly to the sources in which they were produced. As such, they have the potential tounveil the locations of the still unknown sources of UHE cosmic rays. The surface detector of thePierre Auger Observatory is sensitive to UHE neutrinos and photons with energies above 1 EeVand 10 EeV respectively. Inclined air showers (zenith angle 60 or larger) induced by neutrinosof all flavours (downward- going), and “Earth skimming” tau neutrinos (upward-going) can beidentified through the broad time-structure of the signal that is expected to be induced in thedetector. UHE photon-induced air showers can be distinguished from hadronic ones on the basisof observables sensitive to the mass composition of the primary particle. In this talk I will presentthe most recent results from these searches, and discuss the astrophysical implications of thesefindings for the sources of UHE cosmic rays.

Collaboration

Pierre Auger Collaboration

Primary author: OIKONOMOU, Foteini

Presenter: OIKONOMOU, Foteini



28th Texas Symp … / Report of Contributions Time-dependent Pair Halo Emissio …


Time-dependent Pair Halo Emission fromVery-High-Energy Gamma-Ray Sources


Gamma-rays with energy exceeding 100 GeV emitted by extragalactic sources, such as blazars,initiate cascades in the intergalactic medium. The angular and temporal distribution of the cascadephotons that arrive at the Earth depend on the strength and configuration of extragalactic magneticfields (EGMFs) in the line of sight. For weak enough fields, extended emission around the source(halo) is expected to be detectable, and the characteristics (size, energy dependence, and shape)of this emission are a sensitive probe of EGMF strength and correlation length. In this work, wehave, for the first time, performed detailed calculations of the time dependence of such blazarhalos, in a large range of EGMF parameter space, unconstrained by existing data. I will discuss thequantitative constraints that can be imposed on the EGMF from the recent tentative detection ofhalo emission around 24 stacked blazars observed with the Fermi LAT, as well as the constraintsthat can be derived in the absence of such extended emission around GeV and TeV emitting blazars.

Primary author: OIKONOMOU, Foteini

Co-authors: MURASE, Kohta (I); KOTERA, Kumiko (Institut d’Astrophysique de Paris)

Presenter: OIKONOMOU, Foteini



28th Texas Symp … / Report of Contributions Massive neutrinos and their effect …


Massive neutrinos and their effect on the large scalestructure of the Universe


Neutrinos are described as fundamental particles by the standard model of particle physics. Thefact that neutrinos are massive, as demonstrated by neutrino oscillations experiments, point to-wards physics beyond the standard model. Thus, one of the most important questions in modernphysics is: which are the masses of the neutrinos? Current tightest constrain on the sum of theneutrino masses arise from cosmology observables. In order to extract the maximum informationfrom current and future surveys, as well as to avoid introducing biases in the values of the cos-mological parameters, it is of primordial importance to understand, both at the linear and at thefully non-linear order, the impact that massive neutrinos induce on the distribution of matter, ha-los and galaxies. Among the different methods that can be used to carried out this task, N-bodysimulations offer the most accurate picture. In this talk I will show how to run N-body simulationsin cosmologies with massive neutrinos. I will also present some of the effects neutrinos induceon the Universe large scale structure, among then the clustering of matter, the clustering of darkmatter halos, the abundance of halos, the abundance of voids, their impact on the BAO peak andso on.

Primary author: VILLAESCUSA-NAVARRO, Francisco (OATS-INAF)

Presenter: VILLAESCUSA-NAVARRO, Francisco (OATS-INAF)



28th Texas Symp … / Report of Contributions Very fast TeV gamma-ray variabili …


Very fast TeV gamma-ray variability from thenon-aligned AGN IC 310: Insight into Black Hole

LightningsTuesday, December 15, 2015 2:42 PM (21 minutes)

Rapid flux variabilities with time scales of minutes are regularly detected in the very high energy(VHE) gamma-ray emission of blazars during violent flaring periods. Those are generally explainedby the classical shock-in-jet acceleration models, assuming a very large Doppler factor, whichcondenses the intrinsic multi-hours-scale variations into a few minutes for the observer on Earth.This assumption, which requires a large jet Lorentz factor (>10) and very small angle between thejet and the observer (<5 deg), is conceivable for blazars. However, recent observation of rapidvariabilities in the VHE gamma-ray flux from the peculiar radio galaxy IC 310 by MAGIC is verychallenging for the shock-in-jet model. Indeed the jet viewing angle is estimated to lie between 10and 20 deg, and the Doppler boost cannot play a dramatic role. The flux doubling-time measured inNovember 2012 is faster than 5 min and constrains the size of the emission region to be smaller than20% of the gravitational radius of the central black hole. Here, we will present in detail the MAGICobservations and discuss possible alternative models, such as pulsar-like particle acceleration inthe magnetosphere anchored to the plasma surrounding a spinning black hole.

Collaboration

MAGIC

Primary authors: GLAWION, Dorit; SITAREK, Julian (University of Łódź); Prof. MANNHEIM,Karl (Uni Wuerzburg); COLIN, Pierre (MPI fuer Physik)

Co-authors: ROS, Eduardo (Instituto de Fisica Corpuscular (ES)); KRAUSS, Felicia (Uni Wuerzburg); WILMS,Joern (Uni Erlangen-Nuerberg); KADLER, Matthias (Uni Würzburg); SCHULZ, Robert (Uni Wuerzburg)

Presenter: COLIN, Pierre (MPI fuer Physik)

28th Texas Symp … / Report of Contributions Glitches and anti-glitches in accret …


Glitches and anti-glitches in accreting pulsars:expected properties and observability


Glitches have been observed in isolated pulsars, while aclear detection in accretion-powered X-ray pulsars is still lacking.We use the “snowplow” model for pulsar glitches of Pizzochero(2011) and starquake models to determine for the first time theexpected properties of glitches in accreting pulsars. We alsoinvestigate the possibility that anti-glitches occur in accretingpulsars which show accretion-induced long-term spin-up. We findthat glitches caused by quakes in a slow accreting neutron star arevery rare and their detection extremely unlikely. On the contrary,glitches and anti-glitches caused by a transfer of angularmomentum between the superfluid neutron vortices and the non-superfluid component may take place in accreting pulsars moreoften. We calculate the expected maximum jump in angularvelocity of an anti-glitch and we also find that both glitches andanti-glitches in accreting pulsars are expected to have long riseand recovery time scales compared to isolated glitching pulsars.We find that, among accreting pulsars, GX 1+4 is the bestcandidate for the detection of glitches with currently operatingX-ray satellites.

Primary author: DUCCI, Lorenzo (University of Tuebingen)

Co-authors: Prof. SANTANGELO, Andrea (University of Tuebingen); Dr FERRIGNO, Carlo (Uni-versity of Geneva); Prof. PIZZOCHERO, Pierre (Università di Milano); Dr MEREGHETTI, Sandro(INAF-IASF Milan); Dr DOROSHENKO, Victor (IAAT, University of Tuebingen)

Presenter: DUCCI, Lorenzo (University of Tuebingen)



28th Texas Symp … / Report of Contributions Examining Accretion Disk Propert …


Examining Accretion Disk Properties of Sgr A* ViaStellar Wind Interactions


A recent method has been proposed for probing the properties of the accretion disk surroundingSgr A* located at our galactic center. This is based on a study of the collision between the diskfluid and the wind of the star, S2. We expand upon the previous work by constructing a semi-analytical model for the shock formation in the stellar wind. This takes into account the thermalpressure of the disk and employs the conservation of momentum flux in the shocked region forderiving the shape of the shock. Our analysis yields semi-analytical expressions for the system as afunction of the accretion disk density. For typical values of the latter, we find that the temperatureof the shocked stellar wind reaches a few keV. The shocked gas cools via thermal bremsstrahlungemission with a luminosity of ∼ 1033erg/s, assuming solar metallicity. These results have so farbeen validated by numerical simulations and are within the detection range of current instruments.Ultimately, the detection of these interactions can constrain the density of the disk around thepericenter of the orbit of S2, which will occur in 2018.

Primary author: Mr CHRISTIE, Ian (Purdue University)

Co-authors: Prof. GIANNIOS, Dimitrios (Purdue University); Dr PETROPOULOU, Maria (PurdueUniversity); Dr MIMICA, Petar (University of Valencia)

Presenter: Mr CHRISTIE, Ian (Purdue University)



28th Texas Symp … / Report of Contributions Higher-order massive neutrino pe …


Higher-order massive neutrino perturbations inlarge-scale structure


I will present a new first principle approach for higher order perturbation theory for hot andwarm dark matter in large scale structure. The approach is based on a non-linear generalizationof Gilbert’s equation. Combined with standard perturbation theory, it allows to calculate N-pointstatistics of density perturbations in mixed cold+hot dark matter cosmologies. I apply the theory tocompute the leading order bispectrum in a mixed CDM+neutrino universe and use it as benchmarkto test the validity of some simple approximations schemes

Primary author: FÜHRER, Florian (Institut für Theoretische Physik, Universität Heidelberg)

Presenter: FÜHRER, Florian (Institut für Theoretische Physik, Universität Heidelberg)



28th Texas Symp … / Report of Contributions Astrophysical backgrounds in anti …


Astrophysical backgrounds in antiproton searchesfor dark matter


I review the results of a new calculation for the antiproton production by cosmic ray protons andnuclei and discuss the expected theoretical uncertainty. Then I discuss the antiproton flux expectedfrom a local, 2 Myr old SN and the implication for indirect dark matter searches.

Primary author: KACHELRIESS, Michael (NTNU)

Presenter: KACHELRIESS, Michael (NTNU)



28th Texas Symp … / Report of Contributions Cosmic magnetic fields and ways o …


Cosmic magnetic fields and ways of probing themTuesday, December 15, 2015 2:00 PM (25 minutes)

A non-negligible fraction of a Supermassive Black Hole’s (SMBH) rest mass energy gets trans-ported into extragalactic space - by remarkable processes in jets which are not completelyunderstood. The bulk of the energy flow from the SMBH (e.g. 107 M⊙ ) appears to beelectromagnetic, rather than via a particle beam flux. Also, remarkably, these jets contain currentflows that remain largely intact over multi-kpc distances. Accretion disk models have indepen-dently calculated that a ∼ 108 M⊙ SMBH should generate O(1018−19) Ampères in the vicinity ofthe SMBH.I describe the best yet observational estimate of the current flow along the axis of a jet that extendsfrom the nucleus of the active elliptical galaxy in 3C303. This is I ∼ 1018 Ampères at a projected20 kpc from the AGN. This points to the existence of cosmic scale electric circuits. The power flowis P = I2Z, watts, where Z ∼ 30 Ohms, which is O (the impedance of free space), Z (ϵ0, µ0), where(ϵ0, µ0) are the permittivity and magnetic permeability. These, in turn, uniquely determine c. Theelectrical potential drop (∼ 1020 V) across the jet diameter (which is a few times rG of the SMBH)is, interestingly that required to accelerate Ultra High Energy Cosmic Rays (UHECR).Jets and high energy outflows have different progenitors, forms, sizes, luminosities, and ambientenvironments. This talk focuses on electromagnetically dominated (Poynting flux) jets from su-permassive BH’s located in a rarified intergalactic environment - i.e. not in rich galaxy clusters.

Primary author: Prof. KRONBERG, Philipp (University of Toronto)

Presenter: Prof. KRONBERG, Philipp (University of Toronto)



28th Texas Symp … / Report of Contributions The Chiral Magnetic Effect and its …


The Chiral Magnetic Effect and its Role inAstrophysics and Cosmology


We will present work on the chiral magnetic instability in the context of hot neutron stars and itspossible role for magneto genesis in the early Universe. Whether a chiral asymmetry in the elec-tron sector, induced for example by the electroweak interaction, leads to growing helical magneticfields depends on many factors that will be discussed in this talk.

Primary author: SIGL, Guenter (II. Institut für theoretische Physik, Universität Hamburg)

Co-author: Ms LEITE, Natacha (II. Institut für theoretische Physik, Universität Hamburg)

Presenter: SIGL, Guenter (II. Institut für theoretische Physik, Universität Hamburg)



28th Texas Symp … / Report of Contributions Large Scale Structure with interac …


Large Scale Structure with interacting Vacuum: thenon-linear regime in the post-Friedman

approximationMonday, December 14, 2015 4:55 PM (20 minutes)

General-relativistic cosmological models where vacuum interacts with cold dark matter (iV-CDMmodels) maybe a good alternative to the standard LCDM scenario. The post-Friedmann approxi-mation generalises to cosmology post-Newtonian methods and we have used it to extract frame-dragging, a pure GR effect, from standard N-body simulations in LCDM and in f(R) models. Afterbriefly summarising the iVCDM scenario and the post-Friedmann approximation I will discuss itsextension from LCDM to the iVCDM case, concluding with an outlook on future work.

Primary author: BRUNI, Marco (University of Portsmouth)

Presenter: BRUNI, Marco (University of Portsmouth)



28th Texas Symp … / Report of Contributions Simultaneous X-ray and Radio obs …


Simultaneous X-ray and Radio observations ofmode-switching radio pulsars PSR B0943+10 and PSR

B1822-09Wednesday, December 16, 2015 3:15 PM (30 minutes)

With XMM-Newton, GMRT and LOFAR observations of the mode-changing near-aligned pulsarPSR B0943+10 we discovered synchronous switching in the radio and X-ray emission properties(Hermsen et al. 2013). These extraordinary findings were reported to support radio indications forrapid, global changes to the conditions in the magnetosphere. However, there is still no consistentinterpretation for the X-ray mode switching. PSR B1822-09 is a fascinating pulsar exhibiting sim-ilar mode switching in the radio band. Mode switching in the radio emission of PSR B1822-09 isnot only seen in its main-pulse and precursor emissions (like for PSR B0943+10), but also in thatof its inter pulse. The latter switches in anti correlation with the main pulse. Radio data on PSRB1822-09 strongly suggest that it is an orthogonal rotator, but a near-aligned geometry is also dis-cussed in literature. We organised for this pulsar in 2013-2014 a similar campaign of simultaneousXMM-Newton, GMRT, WSRT and Lovell observations. PSR B1822-09 does not show X-ray modeswitching and exhibits X-ray characteristics that differ from those reported for PSR B0943+10, andthat do not support the geometries discussed based on its radio properties. In this presentation wewill compare the results from the two X-ray radio campaigns and discuss these in the context ofcompeting theoretical emission models.

Hermsen et al., 2013, Science 339, 436

Primary author: Prof. HERMSEN, Wim (SRON Netherlands Institute for Space Research, Utrecht,The Netherlands)

Co-authors: Prof. STAPPERS, Ben (Jodrel Bank Centre for Astrophysics, School of Physics and As-tronomy, University of Manchester, UK); Dr MITRA, Dipanjan (National Centre for Radio Astrophysics,Pune, India); Dr WRIGHT, Geoffrey (Astronomy Centre, University of Sussex, Falmer, Brighton, UK); DrHESSELS, Jason (Astronomical Institute ’Anton Pannekoek’, University of Amsterdam, Amsterdam,The Netherlands); Prof. RANKIN, Joanna (Physics Department, University of Vermont, Burlington,USA); Dr VAN LEEUWEN, Joeri (ASTRON, the Netherlands Institute for Radio Astronomy, Dwingeloo,The Netherlands); Dr KUIPER, Lucien (SRON Netherlands Institute for Space Research, Utrecht, TheNetherlands)

Presenter: Prof. HERMSEN, Wim (SRON Netherlands Institute for Space Research, Utrecht, TheNetherlands)



28th Texas Symp … / Report of Contributions Effect of Equation of State on Mag …


Effect of Equation of State on Magnetized BinaryNeutron Star Mergers


In this talk I will present some general relativistic magnetohydrodynamic simulations producedwith the numerical code WHISKY. We have simulated magnetized binary neutron star mergerswith two different Equations of State: ideal-fluid and H4. We have focused in particular on high-mass systems (both equal and unequal-mass ones) that produce after the merger a spinning blackhole surrounded by a magnetized accretion disk. These models are indeed one of the main candi-dates for the central engine of short gamma-ray bursts (SGRBs). I will discuss the possible connec-tion between these models and SGRBs as well as their gravitational wave signal.

Primary author: Mr KAWAMURA, Takumu (University of Trento)

Presenter: Mr KAWAMURA, Takumu (University of Trento)



28th Texas Symp … / Report of Contributions Evolution of a self-gravitating sph …


Evolution of a self-gravitating spherical masslessscalar field on compactified constant mean curvature

hypersurfacesThursday, December 17, 2015 5:15 PM (20 minutes)

I present the numerical evolution of a self-gravitating massless spherical scalar field based on a newcode which implements the 3+1 tetrad formulation of general relativity on compactified constantmean curvature (CMC) hypersurfaces developed by Bardeen, Sarbach and Buchman. The majoradvantage of this formulation is that it allow us to model with high accuracy the scalar radiationat future null infinity, removing the need to impose artificial outer boundary conditions. As atest case of study, I explore the evolution of different initially in-going packets or shells of scalarfields and compare the results to standard results in the literature, including Choptuik’s results oncritical collapse.

Primary author: MORALES, Manuel David (Instituto de Física y Matemáticas - Universidad Mi-choacana de San Nicolás de Hidalgo)

Co-author: Dr SARBACH, Olivier (Instituto de Física y Matemáticas - Universidad Michoacana deSan Nicolás de Hidalgo)

Presenter: MORALES, Manuel David (Instituto de Física y Matemáticas - Universidad Michoacanade San Nicolás de Hidalgo)



28th Texas Symp … / Report of Contributions Blowing in the wind : accretion in …


Blowing in the wind : accretion in high mass X-raybinaries


Compact objects in high mass X-ray binaries (HMXB), where the companion star underfills itsRoche lobe, have been spotted as X-ray emitters, probably due to the presence of a surrounding disc,along with their low mass counterparts (LMXB). However, if the disc formation is well understoodin LMXB where matter is poured through the first Lagrangian point, things get messier in HMXB,especially in Supergiant-HMXB whose number has almost tripled thanks to recent observationswith Integral (Chaty 2011, Walter et al 2015). Indeed, the massive companion stars have denseand fast winds which can lead to a Bondi-Hoyle like accretion (a.k.a. wind accretion) onto thecompact body. Given the variability of the instantaneous mass and angular momentum accretionrates in this configuration, the disc formation is way more uncertain. The observed photometricand spectral variabilities of the flux might reflect transient accretion phases due to orbital scalemodulations like a clumpy wind or non-homogeneous streamlines.

So as to get a better feel of the properties of the subsequently formed disc, we designed a nu-merical setup able to grasp the huge spatial dynamics of the Bondi-Hoyle accretion onto a compactobject for non-relativistic wind velocities (El Mellah and Casse, 2015). From the accretion radius ofthe black hole down to the vicinity of its event horizon, the flow spans up to 5 orders-of-magnitude.Taking the most of the highly parallelized code MPI-AMRVAC, we characterized the flow proper-ties in the axysymmetric configuration, both in terms of observable-related quantities (e.g. massaccretion rates as a function of the Mach number of the unperturbed flow) and in terms of topol-ogy of the sonic surface, confirming the result derived in Foglizzo and Ruffert (1996). We thenintroduced non axysymmetric effects for specific sets of orbital parameters in full 3D simulationsand monitored the formation and permanence of a disc-like structure.

Collaboration

EL MELLAH Ileyk & CASSE Fabien

Primary author: EL MELLAH, Ileyk (Paris 7 Diderot - APC laboratory)

Presenter: EL MELLAH, Ileyk (Paris 7 Diderot - APC laboratory)

28th Texas Symp … / Report of Contributions Non linear evolution of BAO and I …


Non linear evolution of BAO and IR - resummationThursday, December 17, 2015 3:03 PM (21 minutes)

Baryon acoustic oscillations (BAO) provide us with one of the most powerful cosmological probes.However, the BAO are plagued by non-linear effects which must be taken into account. I willdiscuss these effects and their physical impact on correlation functions in real and momentumspaces. I will present a new technique (so-called ‘IR — resummation’) to account for these effects toall orders in standard Eulerian perturbation theory and time-sliced perturbation theory. I will showthat leading and next-to-leading IR — resummation ameliorates remarkably our understanding oftwo-point and higher-point statistics. Finally, I will touch on the contributions of short-wavelenghtperturbations and discuss the possibility of ultraviolet renormalisation.

Primary author: IVANOV, Mikhail (Ecole Polytechnique Federale de Lausanne (CH))

Co-authors: BLAS TEMINO, Diego (CERN); GARNY, Mathias (CERN); SIBIRYAKOV, Sergey (CERN& EPFL & INR RAS)

Presenter: IVANOV, Mikhail (Ecole Polytechnique Federale de Lausanne (CH))



28th Texas Symp … / Report of Contributions Cosmic variance in the nanohertz …


Cosmic variance in the nanohertz gravitational wavebackground


We use large N-body simulations and empirical scaling relations between dark matter halos, galax-ies, and supermassive black holes to estimate the formation rates of supermassive black hole bi-naries and the resulting low-frequency stochastic gravitational wave background (GWB). We findthat uncertainty in the astrophysical scaling relations systematically changes the amplitude of theGWB by a factor of ∼2, and that this range is already constrained by recent pulsar timing arrayupper limits. We investigate the Poisson variance in the amplitude of the GWB for randomly-generated populations of supermassive black holes, finding a scatter of order unity per frequencybin below 10 nHz, and increasing to a factor of ∼10 near 100 nHz. This variance is a result ofthe rarity of the most massive binaries, which dominate the signal, and acts as a fundamentaluncertainty on the amplitude of the underlying power law spectrum. This Poisson uncertaintydominates above 20 nHz, while at lower frequencies it is subdominant to that due to our poor un-derstanding of the astrophysical scaling relations. At very low frequencies, uncertainties relatedto the final parsec problem and the processes which drive binaries to the gravitational wave domi-nated regime may affect both the astrophysical and Poisson variance in the spectrum of the GWB.

Primary author: ROEBBER, Elinore (McGill University)

Presenter: ROEBBER, Elinore (McGill University)



28th Texas Symp … / Report of Contributions Simulations of the Magnetosphere …


Simulations of the Magnetospheres of AccretingMillisecond Pulsars: Torque Enhancement, Spin

Equilibrium, and Jet PowerWednesday, December 16, 2015 5:30 PM (20 minutes)

The interaction of a rotating star’s magnetic field with a surrounding plasma disc lies at the heartof many questions posed by neutron stars in X-ray binaries. I will present global simulations ofthis interaction, performed in the force-free (high-magnetization) limit of relativistic MHD, show-ing the opening of magnetic field lines, the formation and reconnection of magnetospheric currentsheets, and a substantial increase in the spin-down torque applied to the star by the pulsar wind.When the disc conductivity is high, the principal simulation results can be captured in a simpleanalytic model for the disc-opened flux, the torques exerted on the star by the magnetosphere,and the power extracted by the electromagnetic wind. Using this model, I will describe the con-ditions under which the system enters an equilibrium spin state, in which the accretion torqueis instantaneously balanced by the pulsar wind torque alone. For magnetic moments, spin fre-quencies, and accretion rates relevant to accreting millisecond pulsars, the spin-down torque fromthis enhanced pulsar wind can be substantially larger than that predicted by existing models ofthe disc-magnetosphere interaction, and is in principle capable of maintaining spin equilibriumat frequencies less than 1 kHz. This mechanism may account for the non-detection of frequencyincreases during outbursts of SAX J1808.4-3658 and XTE J1814-338, and may be generally respon-sible for preventing spin-up to sub-millisecond periods. If the pulsar wind is collimated by thesurrounding environment, the resulting jet can satisfy the power requirements of the highly rela-tivistic outflows from Cir X-1 and Sco X-1. In this framework, the jet power scales relatively weaklywith accretion rate, and would be suppressed at high accretion rates only if the stellar magneticmoment is sufficiently low; this may be consistent with the absence of soft-state jet quenching insome observed neutron-star X-ray binaries.

Primary author: Dr PARFREY, Kyle (Lawrence Berkeley National Laboratory)

Co-authors: Prof. SPITKOVSKY, Anatoly (Princeton University); Prof. BELOBORODOV, Andrei(Columbia University)

Presenter: Dr PARFREY, Kyle (Lawrence Berkeley National Laboratory)



28th Texas Symp … / Report of Contributions Black Hole Jets from MRI- …


Black Hole Jets from MRI-Generated Magnetic FieldsWednesday, December 16, 2015 4:15 PM (21 minutes)

We propose a scenario for launching relativistic jets from rotating black holes, in which small-scalemagnetic flux loops, sustained by disc turbulence, are forced to inflate and open by differential rota-tion between the black hole and the accretion flow. This mechanism does not require a large-scalenet magnetic flux in the accreting plasma, whose presence in the environment of the central engineis questionable in many jet sources. Estimates suggest that the process could operate effectivelyfor a wide range of systems, and particularly naturally and efficiently when the accretion flowis retrograde. We present the results of general-relativistic force-free electrodynamic simulationsdemonstrating the time evolution of the black hole’s magnetosphere, the cyclic formation of jets,and the effect of magnetic reconnection. The jets are highly variable on timescales ∼ 10-103 rg/c,where rg is the black hole’s gravitational radius. The reconnecting current sheets observed in thesimulations may be responsible for the hard X-ray emission from accreting black holes.

Primary author: Dr PARFREY, Kyle (Lawrence Berkeley National Laboratory)

Co-authors: Prof. BELOBORODOV, Andrei (Columbia University); Prof. GIANNIOS, Dimitrios(Purdue University)

Presenter: Dr PARFREY, Kyle (Lawrence Berkeley National Laboratory)



28th Texas Symp … / Report of Contributions Can Black Holes Be Accelerators o …


Can Black Holes Be Accelerators of SpinningMassive Particles?


It is a well known effect that a rotating black hole can acceleratespinless particles to in principle arbitrary energies.Within the formalism of the Spinning Top it is investigatedto which extend the “corresponding” process is also possible:“Can spinning tops be accelerated by a non-rotating black hole?”

It is found that this is indeed the case.

Primary author: Prof. KOCH, Benjamin (Pontifica Universidad Catolica de Chile)

Presenter: Prof. KOCH, Benjamin (Pontifica Universidad Catolica de Chile)



28th Texas Symp … / Report of Contributions The High Energy cosmic-Radiation …


The High Energy cosmic-Radiation Detection (HERD)Facility onboard China’s Future Space Station


The High Energy cosmic-Radiation Detection (HERD) facility is one of several space astronomypayloads onboard China’s future Space Station, which is planned for operation starting around2020. It is designed as a next generation space facility focused on indirect dark matter search, pre-cise cosmic ray spectrum and composition measurements up to the knee energy, and high energygamma-ray monitoring and survey. HERD is composed of a calorimeter (CALO) surrounded bymicro-strip silicon trackers (STKs) from five sides except the bottom. CALO is made of about 10^4cubes of LYSO crystals, corresponding to 55 radiation lengths and 3 nuclear interaction lengths,respectively. Mont Carlo simulation shows that electrons and photons with a high energy reso-lution (∼ 1% for electrons and photons and 20% for nuclei) and a large effective geometry factor(> 3 m^2sr for electrons and diffuse photons and > 2 m^2sr for nuclei) can be achieved under thisdesign. Moreover, R&D is under way for reading out the LYSO signals with optical fiber coupledto image intensified CCD and the prototype of 1/40 CALO for beam test at CERN at Novemberthis year. Furthermore, the extended design and optimization of HERD for gamma-ray astronomyphysics will be discussed in this contribution.

Collaboration

the HERD collaboration

Primary author: XU, Ming (Chinese Academy of Sciences (CN))

Co-author: Mr XU, Ming (ISDC, University of Geneva)

Presenter: XU, Ming (Chinese Academy of Sciences (CN))



28th Texas Symp … / Report of Contributions Results on light dark matter partic …


Results on light dark matter particles with a lowthreshold CRESST-II detector


CRESST-II is a direct dark matter search using cryogenic detectors based on calcium tungstate.Due to their light nuclei and low energy thresholds these detectors allow for a high sensitivity fordark-matter particles with low masses.

We present data corresponding to an exposure of 52 kg-days obtained by one single detector mod-ule with a very low energy threshold of 307 eV for nuclear recoils. A blind analysis was per-formed on the data set resulting in a significantly improved sensitivity for dark-matter particleswith masses below 3 GeV/c2. Furthermore, this result extends the parameter space covered bydirect dark matter searches to the sub-GeV/c2 mass region.

Collaboration

CRESST collaboration

Primary author: GÜTLEIN, Achim (Austrian Academy of Sciences)

Presenter: GÜTLEIN, Achim (Austrian Academy of Sciences)



28th Texas Symp … / Report of Contributions Reconstruction of the past history …


Reconstruction of the past history of the center ofour Galaxy through X-Ray reflection spectra

simulations.Thursday, December 17, 2015 2:21 PM (21 minutes)

In the centre of our Galaxy lies a super-massive black hole, identified with the radio source Sagit-tarius A. Sagittarius A is quite dim in terms of total radiated energy, having a luminosity that isa factor of lower than its Eddington luminosity. However, there is compelling evidence that thissource was far brighter in the past. This conclusion was derived from the detection of reflectedX-ray emission from the giant molecular clouds in the Galactic centre region. However, the inter-pretation of the reflected emission spectra cannot be done correctly without detailed modelling ofthe reflection process. We have developed a Monte Carlo simulation code in order to fully modelthe complex processes involved in the emerging reflection spectra. The simulated spectra can becompared to real data in order to derive model parameters and constrain the past activity of theblack hole. In particular we apply our results to XMM-Newton, Chandra and INTERGRAL ob-servations of Sgr B2, in order to constrain the position and density of the cloud and the incidentluminosity of the central source.

Primary author: Mr WALLS, Michael (DCU)

Co-authors: GOLDWURM, Andrea; CHERNYAKOVA, Maria (DCU); TERRIER, Regis (C)

Presenter: Mr WALLS, Michael (DCU)



28th Texas Symp … / Report of Contributions Clustering, lensing, and ISW-RS fr …


Clustering, lensing, and ISW-RS from the DEMNUnineutrino simulations


I will present the first set of cosmological simulations produced withinthe “Dark Energy and Massive Neutrino Universe” (DEMNUni) project. Thesesimulations are characterized by L=2 Gpc/h, Npart=2 x 2048^3, a baselineLCDM-Planck cosmology, and four different total neutrino masses, Mnu=0,0.17, 0.3, 0.53 eV, with a degenerate mass spectrum. They are the largestN-body simulations to date with a massive neutrino component treated as anadditional particle type. I will present fully non-linear effects in thepresence of massive neutrinos, extracted from the DEMNUni simulations, andshow how neutrino free-streaming alters not only LSS clustering andlensing, but introduces also an excess of power in the ISW/RS signals, andrelated cross-correlations, at intermediate scales.

Primary author: Dr CARBONE, Carmelita (National Institute for Astrophysics - INAF)

Presenter: Dr CARBONE, Carmelita (National Institute for Astrophysics - INAF)



28th Texas Symp … / Report of Contributions Prospects of constraining primord …


Prospects of constraining primordial magnetic fieldsusing their effects on CMB, LSS and ionization

historyTuesday, December 15, 2015 4:35 PM (20 minutes)

The presence of large scale magnetic fields at different epochs can be probed by their impact ondifferent observables such as the CMB spectrum, primary and secondary CMB anisotropies, matterpower spectrum and 21cm line emission. I will give an overview of these effects together withconstraints from current and future experiments.

Primary author: Dr KUNZE, Kerstin (University of Salamanca)

Presenter: Dr KUNZE, Kerstin (University of Salamanca)



28th Texas Symp … / Report of Contributions Across the Eddington boundary: e …


Across the Eddington boundary: examining discspectra at high accretion rates


There are now strong arguments that many ultraluminous X-ray sources (ULXs) are powered bysuper-Eddington accretion on to stellar remnant black holes. However, a key remaining questionis: how are the classic sub-Eddington and new super-Eddington accretion states related? In anattempt to answer this, we present results from a systematic analysis of samples of the brightestthermal dominant (TD) black hole binaries (BHBs) and the faintest ULXs in the 0.3–10 keV bandpass. We have previously shown that the faintest ULXs tend to have X-ray spectra that are disc-like, but broader than expected for thin accretion discs (broadened disc, or BD, spectra). Here wereport that the TD BHB spectra are similar in shape to the BD ULXs in the 0.3–10 keV band, anddiffer only in luminosity, by a factor of ∼ 10. This broadening may have been missed in previousstudies that looked primarily above ∼ 2 keV. As the Eddington ratios of the TD BHBs are wellconstrained to moderate values, known effects are not expected to produce such broad spectra.This implies there may be a missing physical mechanism in our best accretion disc models. Wediscuss the implications of our results for the BD ULXs. If they were at similar Eddington ratios tothe TD BHBs, then they would most likely contain massive stellar remnant black holes. However,this would require that they were all at close to maximal spin. Instead, the BD ULXs could simplybe a high Eddington ratio extension of the TD state.

Primary author: SUTTON, Andrew (NASA Marshall Space Flight Center)

Presenter: SUTTON, Andrew (NASA Marshall Space Flight Center)



28th Texas Symp … / Report of Contributions Self-similar magnetic, turbulent an …


Self-similar magnetic, turbulent and thermal energyevolution in massive galaxy clusters


Massive galaxy clusters (GC) are filled with a hot, turbulent and magnetisedintra-cluster medium (ICM). They are still forming under the action of gravitational instabilitydriving supersonic accretion flows, which partially dissipate into heat through acomplex network of large scale shocks, while partly excite giant turbulenteddies and cascade. Amongst others turbulence amplifies magnetic energy byway of dynamo action. This pattern of gravitational energy turning kinetic,thermal, turbulent and magnetic is a basic feature of GC hydrodynamics butquantitative modelling remains a challenge.In this contribution we present results from recent high resolution numericalsimulations of structure formation in which the time dependent turbulentmotions of the intracluster medium of a massive galaxy cluster are resolvedand their statistical properties quantified for the first time.Combined with independent state-of-theart results on turbulent dynamo wedetermine without adjustable parameters the thermal,turbulent and magnetic history of giant GC.I will discuss the scale free character of energy structure in the intraclustermedium and how it encodes information about the efficiency of turbulent heating and dynamoaction directly accessible through astronomical observations.

Primary author: Dr MINIATI, Francesco (ETHZ - ETH Zurich)

Co-author: Dr ANDREY, Beresnyak (Nordita)

Presenter: Dr MINIATI, Francesco (ETHZ - ETH Zurich)



28th Texas Symp … / Report of Contributions On the Detection of an Extreme G …


On the Detection of an Extreme GravitationallyRedshifted Fe-line constraining the Rotation of the

Super-Massive Black Hole in Mrk 876Wednesday, December 16, 2015 2:25 PM (22 minutes)

Most galaxies undergo one or more eras of Active Galactic Nucleus (AGN) activity throughouttheir existence. During this era their environment around the central super-massive black holeemits from X-ray to soft gamma-ray energies. Therefore these spectra and their features carrythe information of the extreme gravitational conditions. However these spectral features can betransient and shifted to unexpected energies making their detection difficult.We present our recent results of a case study on the AGN Mrk 876. The detection of a transientand extreme gravitationally redshifted Fe-line allows us to find its emission mechanism, therebyconstraining the rotation of the super-massive black hole in the center of Mrk 876. This findingtogether with a morphological study of the source allows for conclusions on the mechanism thatswitched on the AGN activity in Mrk 876.

Primary author: BOTTACINI, Eugenio (Stanford University)

Presenter: BOTTACINI, Eugenio (Stanford University)



28th Texas Symp … / Report of Contributions Diffuse emissions from radio thro …


Diffuse emissions from radio through microwaves togamma rays


Diffuse emission has dramatically increased the interest of the astrophysical community, due torecent detailed observations by Planck, Fermi-LAT, H.E.S.S. and VERITAS. Unfortunately disentan-gling and characterizing this diffuse emission strongly depends on uncertainties in the knowledgeof unresolved sources, cosmic rays, matter, radiation fields, and magnetic fields.We discuss here the diffuse emission produced by cosmic rays and its uncertainties. Thanks to ob-servations and comparison of sophisticated models of the diffuse emission from radio through mi-crowaves to gamma rays, we are gaining important insights on CR spectra and intensities through-out the Galaxy and in the inner heliosphere.

Primary author: ORLANDO, Elena (Stanford University)

Presenter: ORLANDO, Elena (Stanford University)



28th Texas Symp … / Report of Contributions Constraining sterile neutrinos wit …


Constraining sterile neutrinos with lyman alphaforestTuesday, December 15, 2015 4:57 PM (21 minutes)

We reconsider the problem of determining the warmness of dark matterfrom the growth of large scale structures. In particular, we havere-analyzed the previous work of Viel et al 2013, based on highresolution Lyman-alpha forest spectra. In fact, the flux powerspectrum exhibits a cut-off below ~ 1.5 Mpc/h, this may be explainedby the temperature of the intergalactic medium (IGM) or be due to thefree-streaming of dark matter particles. We show that if the IGMtemperature at high redshifts was low enough (rising at later times)then the data indeed prefer warm dark matter. Assuming this broaderrange of thermal histories, we find that mWDM >= 2.1 keV for thermalrelic at 95% CL (mNRP >= 12 keV for non-resonantly produced sterileneutrino). We discuss an independent method that would allow toexclude the influence of WDM on observable small-scale structures, orwould lead to the discovery of WDM. We also determine values oflepton asymmetry making resonantly produced 7 keV sterile neutrinosconsistent with the data.

Primary author: Dr GARZILLI, Antonella (Leiden University)

Co-authors: RUCHAYSKIY, Oleg (Ecole Polytechnique Federale de Lausanne (CH)); BOIARSKYI,Oleksii (Leiden University (NL))

Presenter: Dr GARZILLI, Antonella (Leiden University)



28th Texas Symp … / Report of Contributions High-mass X-ray binary systems t …


High-mass X-ray binary systems through the eyes ofINTEGRAL


Review of the most prominent results obtained with the INTEGRAL observatory for high-massX-ray binary systems (HMXBs) is presented. Hard X-ray observations by INTEGRAL have broad-ened significantly our knowledge about X-ray binaries in the Milky Way. During dozen years theobservatory discovered new types and populations of binary systems, like supergiant fast x-raytransients, heavily obscured sources, has permitted the studies of cyclotron resonance scatteringfeatures with the high resolution for several persistent and transient pulsars. The unique charac-teristics of INTEGRAL in a combination with its long life time as well as deep observations of theGalactic plane played a fundamental role for building a complete catalogue of HXMBs, to studythe different populations of these systems in our Galaxy, to measure their spatial distribution andluminosity function and to constrain some of the time scales and processes driving their birth andevolution.

Primary author: LUTOVINOV, Alexander (Space Research Institute)

Co-authors: BOZZO, Enrico (University of Geneva); WALTER, Roland (University of Geneva); DrTSYGANKOV, Sergey (Tuorla Observatory, University of Turku)

Presenter: LUTOVINOV, Alexander (Space Research Institute)



28th Texas Symp … / Report of Contributions A Universal velocity dispersion pr …


A Universal velocity dispersion profile for pressuresupported systems: evidence for MONDian gravity

across 12 orders of magnitude in massTuesday, December 15, 2015 4:35 PM (20 minutes)

For any MONDian extended theory of gravity where the rotation curves of spiral galaxies areexplained through a change in physics rather than the hypothesis of dark matter, a generic dy-namical behaviour is expected for pressure supported systems: an outer flattening of the velocitydispersion profile occurring at a characteristic radius, where both the amplitude of this flat veloc-ity dispersion and the radius at which it appears are predicted to show distinct scalings with thetotal mass of the system. By carefully analysing dynamics of globular clusters, elliptical galaxiesand galaxy clusters, we are able to significantly extend the astronomical scales over which MON-Dian gravity has been tested, from those of spiral galaxies, to the much larger range covered bypressure supported systems. We show that a universal projected velocity dispersion profile accu-rately describes various classes of pressure supported systems, and further, that the expectationsof extended gravity are met, across twelve orders in magnitude in mass. These observed scalingsare not expected under dark matter cosmology, and would require particular explanations tunedat the scales of each distinct astrophysical system.

Collaboration

X. Hernández, R. Durazo, B. Cervantes-Sodi, H.J. Ibarra-Medel, O. Lopez-Cruz

Primary author: Dr HERNANDEZ, Xavier (Instituto de Astronomía, Universidad Nacional Autónomade México)

Co-authors: Dr CERVANTES-SODI, Bernardo (Centro de Radioastronomía y Astrofísica, Universi-dad Nacional Autónoma de México); Dr IBARRA-MEDEL, Hector (Instituto de Astronomía, UniversidadNacional Autónoma de México); Dr LOPEZ-CRUZ, Omar (Instituto Nacional de Astrofísica, Óptica yElectrónica); Mr DURAZO, Reginaldo (Instituto de Astronomía, Universidad Nacional Autónoma deMéxico)

Presenter: Mr DURAZO, Reginaldo (Instituto de Astronomía, Universidad Nacional Autónoma deMéxico)



28th Texas Symp … / Report of Contributions On the low magnetic fields of milli …


On the low magnetic fields of millisecond pulsarsWednesday, December 16, 2015 6:20 PM (15 minutes)

Millisecond pulsars (MSPs) are old and very fast rotating neutron stars (NS) with much weakermagnetic fields than the younger classical pulsars and magnetars. Most MSPs are in binary systems,suggesting a “recycling scenario”, in which a classical pulsar accretes matter from its companionand as a consequence spins up. Although this scenario explains the fast rotation, it is not clearyet how the magnetic field is reduced. The standard scenarios attribute it to the accretion process,either by increasing the temperature and thus the resistivity of the crust, leading to dissipation ofthe currents (assumed to flow in the crust), or by diamagnetic screening of the field by the accretedmatter (which is implausible, because of magnetic buoyancy and the stiffness of the magnetic fieldlines). We examine an alternative hypothesis, in which ambipolar diffusion expels the magneticflux from the neutron star core, in this way driving its decay. This process is particularly effectiveduring the long period in which the neutron star has cooled substantially and has not yet startedaccreting, making the final magnetic field dependent on the evolutionary time of the companionstar (and thus its initial mass), and naturally yielding field strengths of the observed magnitudes.Our predictions also appear to be consistent with the observed distribution of magnetic fields ofmillisecond pulsars according to their companion type: He white dwarfs, CO white dwarfs, orneutron stars.

Primary author: Ms CRUCES, Marilyn (Instituto de Astrofísica, Pontificia Universidad Católica deChile)

Co-authors: Dr REISENEGGER, Andreas (Instituto de Astrofísica, Pontificia Universidad Católicade Chile); Dr TAURIS, Thomas (Argelander Institut für Astronomie, Universität Bonn)

Presenter: Ms CRUCES, Marilyn (Instituto de Astrofísica, Pontificia Universidad Católica de Chile)



28th Texas Symp … / Report of Contributions Fermi Bubbles as a probes of Galac …


Fermi Bubbles as a probes of Galactic haloenvironment


Fermi bubbles are giant gamma-ray structures seen above and below the Galactic plane with char-acteristic size of order of 10 kpc. They also show very good correlation with the microwave emis-sion discovered by the WMAP telescope and the residual diffuse emission in the range above 30GHz found by the Planck satellite. Correlation between gamma-ray emission observed by Fermiand radio emission observed by Plank implies the presence of high-energy particles in the area cov-ered by Fermi bubbles. These particles may be produced in the Galactic center or accelerated in-situ.Since size of Fermi Bubbles is extremely large, potential transport and acceleration processes arestrongly affected by Galactic halo environment and also can affect distribution of Galactic cosmicrays. Thus Fermi Bubbles can be considered as a interesting probe of the magnetic field strengthand cosmic ray concentration in the Galactic Halo. We provide a multi-wavelength analysis to setsome restrictions on potential models of Fermi bubbles as well as on the propagation of cosmicrays in the central region of our Galaxy.

Primary authors: CHERNYSHOV, Dmitriy (Lebedev’s Institute of Physics, Moscow, Russia); Prof.CHENG, Kwong Sang (The University of Hong Kong); Prof. DOGIEL, Vladimir (Lebedev’s Insitute ofPhysics)

Presenter: CHERNYSHOV, Dmitriy (Lebedev’s Institute of Physics, Moscow, Russia)



28th Texas Symp … / Report of Contributions Constraints on induced gravity da …


Constraints on induced gravity dark energy modelsTuesday, December 15, 2015 2:53 PM (26 minutes)

We study the predictions for structure formation in an induced gravitydark energy modelwith a quartic potential. By developing a dedicated Einstein-Boltzmanncode, we studyself-consistently the dynamics of homogeneous cosmology and of linearperturbationswithout using any parametrization,accurately recovering the quasi-static analytic approximation in thematter dominated era.We use CMB anisotropies data and a compilation of BAO data to constrainthe couplingγ to the Ricci curvature and the other cosmological parameters.By connecting the gravitational constant in the Einstein equation to the onemeasured in a Cavendish-like experiment, we find γ < 0.0012 at 95 %confidence level with Planck 2013 and BAO data, and present theupdated Planck 2015 constraint. Because of a degeneracy between γ

and the Hubble constant H0, we show how larger values for γ areallowed, but not preferred at a significant statistical level,when local measurements of H0 are combined in the analysis with Planck data.We also extend the analysis and constraints to a simple monomial potentialwith a positiveexponent.

Primary author: BALLARDINI, Mario (University of Bologna)

Presenter: BALLARDINI, Mario (University of Bologna)

28th Texas Symp … / Report of Contributions Probing violations of slow-roll infl …


Probing violations of slow-roll inflation at thelargest observable scales with future galaxy surveys


The predictions of the simplestinflationary models, such as a flat Universe and Gaussian adiabaticperturbations with a red tilt, provide a remarkable good fit to the mostrecent measurements of CMB temperature andpolarization anisotropies. Nevertheless, deviations from a simplepower-law spectrum provide a better fit to Planck temperature anisotropiesdata, in particular on the largest scales, i.e. at k < 0.008 Mpc−1,although at a non-statistical significant level because of cosmicvariance. We study the capability of future galaxy surveys as EUCLID andother experiments to distinguish possible deviations from a simplepower-law for primordial perturbation on these large scales.

Primary author: BALLARDINI, Mario (University of Bologna)

Presenter: BALLARDINI, Mario (University of Bologna)

28th Texas Symp … / Report of Contributions The Large European Array for Pul …


The Large European Array for Pulsars: a leap of theEPTA for gravitational wave detection


Searching for gravitational waves has nowadays been a vital astrophysical experiment in gravityand pulsar timing array (PTA) constitutes the major effort in low frequency regime. The detectionof gravitational waves with PTAs relies on the technique of high precision pulsar timing currentlyachieved with the 100-m class radio telescopes. In this talk, I will present an overview of theLarge European Array for Pulsars (LEAP), a key project within the European PTA collaboration tooptimally use the largest radio telescopes in Europe to detect gravitational waves. I will first givea brief introduction of the current state-of-the-art EPTA timing observations. I will then providea description of LEAP’s experimental design and an update on its latest status. In addition, I willshow the preliminary results on pulsar timing and prospect the contribution of LEAP data into theentire EPTA database, in the light of new limits on gravitational wave background and even thefirst detection. Finally, I will mention the studies with LEAP on instability of pulsar profiles whichwill limit the achievable precision of pulsar timing with the next generation of radio telescopes,e.g., the Square-Kilometre-Array.

Primary author: Dr LIU, Kuo (Max-Planck-Institute for Radio Astronomy)

Presenter: Dr LIU, Kuo (Max-Planck-Institute for Radio Astronomy)



28th Texas Symp … / Report of Contributions Transient dynamics of vortices in …


Transient dynamics of vortices in relativistic regionsof accretion disks around black holes.


This work is related to one of the major unsolved problems in the theory of accretion disks:the problem of pure hydrodynamical origin of effective viscosity in their interiors.If it were solved, we would have a general alternative to the well-known conception ofsupercritical turbulence excited by magneto-rotational instability. As has been widely discussedby fluid physicists since early 1990s, the onset and sustenance of sub-critical turbulence in a spec-trally stable shear flow may occur through the so called ‘bypass’ scenario,when turbulent energy is extracted from the background motion by transiently growing perturba-tions which are crucially different from modes of perturbations. Homogeneous Keplerian flow, asa model of non-magnetic and non-relativistic thin accretion disk, proved to be the moststable among a variety of differentially rotating flows: it has been shown previously, thattransient growth of perturbations, sufficiently large to generate turbulence, can be produced onlyat Reynolds number beyond 10^6 - 10^7. However, in most of the preceding studies only vorticeswith length-scales less than the disk thickness have been considered in the context of transientgrowth phenomenon. Here, we discuss a different type of transiently growing perturbations withazimuthal wavelengths larger than the disk thickness. It turns out, that growth of such perturba-tions becomes greatly larger as one includes general and special relativistic corrections in Keplerianmotion. We suggest that such perturbations, which we refer to as thelarge-scale vortices, may substantially reduce the critical Reynolds number for the onset of turbu-lence in relativistic regions of accretion disks around black holes.

Primary author: ZHURAVLEV, Viacheslav

Presenter: ZHURAVLEV, Viacheslav



28th Texas Symp … / Report of Contributions Using millisecond pulsars to calibr …


Using millisecond pulsars to calibrate XMM/Newtononboard clock


The XMM-Newton space telescope is capable of 30-microsecond time resolution but its onboardclock drifts, for example due to changes in temperature. Current calibration documentation onlyprovides an upper limit on the clock drift of 10^-8, but observations of X-ray millisecond pulsars(MSPs) suggest that it should be more stable.

Using kilo-second XMM-Newton observations of MSPs taken with the EPIC pn-camera in fast tim-ing mode in addition to radio timing measurements from the ATNF pulsar catalog for J1939+2134(641.9 Hz), J0437-4715 (173.6 Hz), J0218+4232 (430.4 Hz) and J0534+2200 (29.9 Hz), we analyzedthe pulse shape for each object with the aim to detect the broadening in the profile produced for alinear clock drift through the use of the statistical H-test plus minimization methods. Our resultssuggest that the clock is much more stable than what was previously claimed in the literature.

A well-established clock stability would permit to derive physical quantities with a properly un-derstood accuracy and perform interesting measurements in accreting X-ray millisecond pulsars(e.g. spin-down rate), transients, among others.

Primary author: Ms CRUCES, Marilyn (Instituto de Astrofísica, Pontificia Universidad Católica deChile)

Co-authors: Dr ARCHIBALD, Anne (ASTRON, Netherlands Institute for Radio Astronomy); DrKONDRATIEV, Vlad (ASTRON, Netherlands Institute for Radio Astronomy)

Presenter: Ms CRUCES, Marilyn (Instituto de Astrofísica, Pontificia Universidad Católica de Chile)



28th Texas Symp … / Report of Contributions Evolution of luminosity-linearsize …


Evolution of luminosity-linearsize relation forsources with steep radio spectrum


We consider four samples of steep-spectrum radio sources from our catalogue UTR-2 at the decame-ter band. These contain galaxies and quasars of both spectral types - with linear steep spectrumand break steep spectrum. To obtain the relation of low-frequency luminosity, at the frequency 25MHz, L_25 and linear size R of sample objects we determine one at the different redshift ranges atthe frame of LambdaCDM Universe model. The derived relatios show positive power trend (L_25 ~R^n, n = 0.5….2.0) for galaxies and quasars. Since the object’s luminosity ratio for monochromaticluminosities at different frequency ranges is independent from the Universe model, one is exam-ined on the luminosity ratio-linear size relation. For the purpose of estimate on the linear size’scosmological evolution, we determine linear size-redshift relations at the narrow luminosity bins(R ~ (1+z)^k, k = 0.7….1.87) in our samples. It is very interesting, that obtained luminosity ratio-linear size relations at higher frequency ranges (infrared, X-ray) display two branches of evolutionof steep-spectrum radio sources.

Primary author: Dr MIROSHNICHENKO, Alla (Institute of Radio Astronomy, NAS of Ukraine)

Presenter: Dr MIROSHNICHENKO, Alla (Institute of Radio Astronomy, NAS of Ukraine)



28th Texas Symp … / Report of Contributions Pulsar observations with the MAG …


Pulsar observations with the MAGIC telescopesMonday, December 14, 2015 4:15 PM (20 minutes)

Although more than 150 gamma-ray pulsars are known in GeV band, their spectra roll off above10 GeV and only two pulsars are detected at about 50 GeV, namely Crab and Vela. There is also alarge difference between Crab and Vela. Crab spectrum is extending above 1 TeV, while Vela has avery soft spectrum, becoming almost undetectable at 100 GeV.In order to further understand the emission mechanism of pulsars, it is necessary to continuesearch pulsars above 50 GeV with imaging atmospheric Cherenkov telescopes. In this talk, we willreport on the recent observations of Crab and Geminga pulsars by the MAGIC telescopes, alongwith the analysis results of Fermi-LAT data. The future prospect on the gamma-ray observationwith MAGIC will also be shown.

Collaboration

MAGIC

Primary author: Dr SAITO, Takayuki (Kyoto University)

Co-authors: GALINDO, Daniel (University of Barcelona); FIDALGO, David; DE ONA WILHELMI,Emma (CSIC-IEEC); ZANIN, Roberta (Universitat de Barcelona); BONNEFOY, Simon; Dr LÓPEZMOYA, marcos

Presenter: Dr SAITO, Takayuki (Kyoto University)



28th Texas Symp … / Report of Contributions Dark matter ultracompact minihal …


Dark matter ultracompact minihalos and thesmall-scale early Universe


In this talk I will discuss recent efforts to detect dark matter ‘ultracompact minihalos’ (UCMHs),including a novel utilisation of gravitational time-delay lensing with pulsars. Recently proposed asa type of small-scale dark matter structure, UCMHs are formed from large overdensities in the veryearly Universe. They have been shown to be able to persist through to the present day, providinga unique opportunity to investigate the conditions of the Universe at early times. I will presentrecent results constraining the number of UCMHs within the Milky Way, and discuss their impliedlimits on three processes that lead to their formation: increased primordial power on small scales,primordial non-Gaussianity, and the presence of high-tension cosmic string loops.

Primary author: CLARK, Hamish (University of Sydney)

Co-authors: Prof. LEWIS, Geraint (University of Sydney); Dr SCOTT, Pat (Imperial College Lon-don)

Presenter: CLARK, Hamish (University of Sydney)



28th Texas Symp … / Report of Contributions Correlation study of spectral para …


Correlation study of spectral parameters ofNS-HMXBs with Suzaku


We present a broadband spectral analysis of classical HMXBs (supergiant andBe/X-ray binaries) and Supergiant Fast X-ray Transients (SFXTs) using datafrom XIS and PIN instruments onboard Suzaku. After fitting the X-ray spectraof 36 sources with a single model: a powerlaw and a high energy cutoff (whererequired), we studied the correlation between various spectral parameters.We present the following results: (i) We find a linear correlation betweenthe cyclotron line energy and the cutoff energy as is previously reported inliterature using RXTE and Ginga data (for cyclotron line energy less than35 keV). Using Suzaku obervations, though, we find that there is more thanone slope of variation between the two quantities. (ii) The variation of cutoffenergy with luminosity indicate that NS-HMXBs seem to be divided intotwo classes following two different trends. This division is not on the basisof different beaming mechanism, as can be studied from the pattern of theirpulse profiles. These two groups, notably, show two different patterns whenthe variation of their photonindex is studied against their cutoff energies. (iii)As seen for LMXBs, we note an anticorrelation between the spectral index andluminosity. (iv) Unlike previous works, we do not see anticorrelation betweenthe X-ray luminosity and the equivalent width of Kα lines (Baldwin effect).(vi) The equivalent width and the iron Kα line flux is smaller in SFXTs thanin classical NS-HMXBs.

Collaboration

Raman Research Institute, Bangalore, India & ISDC, University of Geneva, Switzerland

Primary author: Ms PRADHAN, Pragati (St. Joseph’s College, Darjeeling, India & North BengalUniversity, Siliguri, India)

Co-authors: Dr PAUL, Bikash (North Bengal University, Raja Rammohanpur, District Darjeel-ing-734013, West Bengal, India); Dr PAUL, Biswajit (Raman Research Institute, Sadashivnagar, Ban-galore-560080, India); Dr BOZZO, Enrico (ISDC, University of Geneva, Chemin d’Ecogia 16, Versoix,1290, Switzerland)

Presenter: Ms PRADHAN, Pragati (St. Joseph’s College, Darjeeling, India & North Bengal University,Siliguri, India)



28th Texas Symp … / Report of Contributions Supermassive black hole binary ca …


Supermassive black hole binary candidates - Quasarswith optical periodicity in the Palomar Transient

Factory

Supermassive Black Hole Binaries (SMBHBs) are the natural consequence of galaxy mergers andshould be fairly common in galactic nuclei, especially at close separations, where they are expectedto spend most of their lifetime. Hydrodynamical simulations of circumbinary disks predict that themass accretion rate onto the BHs and thus the brightness is periodically modulated at the orbitalperiod of the binary. We perform a systematic search for quasars that exhibit optical periodicity,in the photometric database from the Palomar Transient Factory. We statistically identify severalSMBHB candidates at sub-parsec separations.

Primary author: CHARISI, Maria (Columbia University)

Presenter: CHARISI, Maria (Columbia University)


28th Texas Symp … / Report of Contributions Electromagnetic Emission from Co …


Electromagnetic Emission from CompactSupermassive Black Hole Binaries


In this talk, I will discuss possible characteristics ofelectromagnetic (EM) emission from supermassive black hole (SMBH)binaries. In particular, any detectable EM emission is likely to betime-variable, and contain unique spectral signatures, which shouldaid identifying SMHB binaries. I will discuss recent hydrodynamicalsimulations, which suggest quasiperiodic modulations in the accretionrate onto the BHs prior to coalescence. These time-variable EMsignatures may be used to identify unique counterparts ofgravitational wave sources expected to be detected by (e)LISA and byPulsar Timing Arrays, or to discover binary SMBHs in time-domain EMsurveys. As an example of the latter, the quasar PG1302 was recentlydiscovered to have a 5-yr periodic optical variability. I willcomment on the interpretation of this quasar as a SMBH binarycandidate and its implications.

Primary author: Prof. HAIMAN, Zoltan (Columbia University)

Presenter: Prof. HAIMAN, Zoltan (Columbia University)



28th Texas Symp … / Report of Contributions Dynamical mass ejection from bla …


Dynamical mass ejection from black hole-neutronstar binaries


In recent years, mass ejection from compact binary coalescences has been getting a lot more at-tention. Neutron-rich material ejected from neutron stars during such a coalescence event are in-creasingly recognized as the most promising site of the rapid process (r-process) nucleosynthesis.Mass ejection will also be the primary agent for driving electromagnetic radiation from compact bi-nary mergers, or electromagnetic counterparts to gravitational waves. Simultaneous detection ofelectromagnetic counterparts with gravitational waves is eagerly desired, particularly for accuratesource localization. Because mass ejection from black hole-neutron star binaries is a violent phe-nomenon involving disruption of neutron stars, numerical relativity is the only reliable approachfor theoretical investigation. In this talk, we present our latest results for dynamical mass ejec-tion from the black hole-neutron star binary merger obtained by numerical-relativity simulations.We also discuss possible electromagnetic counterparts from the anisotropic dynamical ejecta fromblack hole-neutron star binaries.

Primary author: Dr KYUTOKU, Koutarou (RIKEN)

Co-authors: Dr OKAWA, Hirotada (Waseda University); Prof. TANIGUCHI, Keisuke (University ofthe Ryukyus); Prof. IOKA, Kunihito (KEK); Prof. SHIBATA, Masaru (Kyoto University)

Presenter: Dr KYUTOKU, Koutarou (RIKEN)



28th Texas Symp … / Report of Contributions Fast luminous blue transients from …


Fast luminous blue transients from newborn blackholesTuesday, December 15, 2015 3:03 PM (21 minutes)

Newborn black holes in collapsing massive stars can be accompanied by a fallback disc. The accre-tion rate is typically super-Eddington and strong disc outflows are expected. Such outflows couldbe directly observed in some failed explosions of compact (blue supergiants or Wolf-Rayet stars)progenitors, and may be more common than long-duration gamma-ray bursts. Using an analyti-cal model, we show that the fallback disc outflows produce blue UV-optical transients with a peakbolometric luminosity of ˜ 1042-43 erg s- 1 (peak R-band absolute AB magnitudes of -16 to -18)and an emission duration of ˜ a few to ˜10 d. The spectra are likely dominated intermediate masselements, but will lack much radioactive nuclei and iron-group elements. The above properties arebroadly consistent with some of the rapid blue transients detected by Panoramic Survey Telescope& Rapid Response System and Palomar Transient Factory. This scenario can be distinguished fromalternative models using radio observations within a few years after the optical peak.

Primary author: Dr KASHIYAMA, Kazumi (University of California, Berkeley)

Presenter: Dr KASHIYAMA, Kazumi (University of California, Berkeley)



28th Texas Symp … / Report of Contributions Accretion of a relativistic kinetic g …


Accretion of a relativistic kinetic gas into a blackhole


We analyze the accretion of gas into a black hole background space-time in the context of relativis-tic kinetic theory. The state of the gas is described by a distribution function which has to satisfythe general relativistic Boltzmann equation.In the first part of this work, we describe a method to find the most general solution of this equationin the collisionless case.

In the second part, we apply our result to the case of a radial flow propagating on a nonrotatingblack hole. We compute the accretion rate and compare it to the one of the Michel fluid flowsolution, clarifying previous results in the literature.

Collaboration

Olivier Sarbach

Primary authors: Mr SARBACH, Olivier (IFM-UMICH); Ms RIOSECO, Paola (IFM-UMICH)

Presenter: Ms RIOSECO, Paola (IFM-UMICH)



28th Texas Symp … / Report of Contributions Cosmological nonlinear density an …


Cosmological nonlinear density and velocity powerspectra


We present the leading order nonlinear density and velocity power spectraincluding the vector- and tensor-type perturbation simultaneously excitedby the scalar-type perturbation in nonlinear order.Concerning density and velocity perturbations of the pressureless matterin perturbation regime well inside of matter-dominated epoch, we show thatpure Einstein’s gravity contributions appearing from the third order areentirely negligible in all scales.

Primary author: Prof. HWANG, Jai-chan (Kyunpook National Univ.)

Co-author: Dr NOH, Hyerim (Korea Astronomy and Space Science Institute)

Presenter: Prof. HWANG, Jai-chan (Kyunpook National Univ.)



28th Texas Symp … / Report of Contributions The accretion-ejection connection …


The accretion-ejection connection in the Galacticblack hole candidate X-ray binary MAXI J1836-194


There is a universal connection between the accretion and ejection phenomena that are observedin black holes across the mass scale. Quantifying this relationship is the first step in understand-ing how jets are launched, accelerated and collimated. X-ray binaries are ideal systems to studythis relationship, as they evolve on human timescales. In outburst, their luminosities increase byseveral orders of magnitude, with the X-ray emission from the accretion disk and the radio emis-sion from the relativistic jets undergoing dramatic, coupled changes. I will present the results of amultiwavelength radio through to X-ray observing campaign of the Galactic black hole candidateX-ray binary MAXI J1836-194 during its 2011 outburst. Our simultaneous observations provide anunprecedented insight into the processes occurring around a black hole during outburst, allowingus to track the evolution of the launching region of the jet as the accretion flow changes. This willhelp to understand the launching of accretion-powered jets on all scales, from X-ray binaries totheir larger-scale analogues, AGN.

Primary author: Dr RUSSELL, Thomas (ICRAR/Curtin University)

Co-authors: Prof. RUSSELL, Dave (New York University Abu Dhabi); Dr ALTAMIRANO, Diego(University of Southampton); Dr MILLER-JONES, James (ICRAR/Curtin University); Dr CURRAN, Pe-ter (ICRAR/Curtin); Dr SORIA, Roberto (ICRAR-Curtin University); MARKOFF, Sera (University ofAmsterdam)

Presenter: Dr RUSSELL, Thomas (ICRAR/Curtin University)



28th Texas Symp … / Report of Contributions A Pulsar Wind Nebula Origin for L …


A Pulsar Wind Nebula Origin for Luminous TeVSource HESS J1640-465


TeV gamma-rays indicate the presence of extremely high-energy particles. While many discreteTeV sources have been identified in the Galactic plane, the origin of these particles is often unclear.This is especially true for HESS J1640-465, among the most luminous TeV sources in the MilkyWay, which is coincident with both a radio supernova remnant and an energetic X-ray pulsar andpulsar wind nebula (PWN). In this talk, I will present the results of a recent Chandra observationof this source, which indicates the PWN is considerably larger and more X-ray luminous thanpreviously thought, and fit to its broadband spectral energy diagram assuming a PWN origin forthe observed X-ray and gamma-ray emission, which constrains both the spectrum of particlesaccelerated in this source and the birth properties of the central neutron star. These results areimportant for determining both the origin of the gamma-rays detected from this source, and howthe production of the highest energy leptons in the galaxy.

Primary author: D GELFAND, Joseph

Presenter: D GELFAND, Joseph



28th Texas Symp … / Report of Contributions Indirect Dark Matter searches with …


Indirect Dark Matter searches with the ASTRImini-array in the framework of the Cherenkov

Telescope ArrayWednesday, December 16, 2015 6:36 PM (3 minutes)

Nowadays there are compelling evidences at several astrophysical scales for a large (~85%), dark,non-baryonic and non-relativistic component of the matter density of the Universe. The questto explain the nature of Dark Matter (DM) represents a paramount issue of modern fundamentalphysics and astrophysics. The non-baryonic DM is compatible with a gas of cold and weaklyinteracting massive particles (WIMPs) expected to have a mass in the range between O(10)GeVand O(100)TeV. One of the most promising approaches to shed light on WIMPs is to search forsignatures of DM annihilation/decay into Standar Model particles from regions of the sky believedto be highly DM dominated, such as the Galactic Centre, clusters of galaxies, and dwarf spheroidalgalaxies (dSphs) of the Milky Way. Among final DM annihilation/decay states, a flux of gammarays tracing back to astrophysical sources is expected at energies up to the DM mass, which couldbe accessible by Imaging Atmospheric Cherenkov Telescopes (IACTs). In this contribution, wepresent prospects on indirect DM searches from different optimal targets in the TeV mass regionwith the ASTRI mini-array, a Cherenkov Telescope Array’s (CTA) precursor, composed of nineASTRI small-sized, dual-mirror telescopes and proposed to be installed at the CTA southern site.

Collaboration

ASTRI Collaboration and CTA Consortium

Primary author: Dr LOMBARDI, Saverio (OAR-INAF, ASDC)

Co-authors: Dr STAMERRA, Antonio (OATO-INAF, SNS-Pisa); Dr BIGONGIARI, Ciro (OATO-I-NAF); ASTRI, Collaboration (http://www.brera.inaf.it/astri/); CTA, Consortium (http://www.cta-observatory.org); DrBROCATO, Enzo (OAR-INAF); Dr DI PIERRO, Federico (OATO-INAF); Dr ANTONELLI, Lucio Angelo(OAR-INAF, ASDC); GIAMMARIA, Paola (Univaq L’Aquila, OAR-INAF)

Presenter: Dr LOMBARDI, Saverio (OAR-INAF, ASDC)



28th Texas Symp … / Report of Contributions Rotation profile of neutron star m …


Rotation profile of neutron star merger remnantsThursday, December 17, 2015 3:03 PM (21 minutes)

A large number of publications model hyper-massive neutron stars (i.e. neutron stars with totalmass exceeding the maximum allowed for a uniformly rotating star) produced in binary neutronstar mergers by assuming a rotation profile with a rapidly rotating core. We confront such modelswith results of general relativistic hydrodynamic simulations which exhibit a slowly rotating coreinstead. Our simulations apply tabulated nuclear physics equations of states including thermaland composition effects, but do not consider neutrino radiation. We investigate the contributionof thermal effects on the structure and short-term stability of the remnant. Further, we discussif under-densities caused by hot spots contribute to the gravitational wave signal, as well as theinfluence of the differential rotation on hot spots.

Primary author: KASTAUN, Wolfgang (Trento University)

Presenter: KASTAUN, Wolfgang (Trento University)



28th Texas Symp … / Report of Contributions Making the Heaviest Elemens in t …


Making the Heaviest Elemens in the UniverseMonday, December 14, 2015 3:18 PM (27 minutes)

The origin of the heavy elements made by the rapid neutron-capture process (”r-process”) is notfully understood, yet. Different sources have been proposed, e.g., core-collapse supernovae as wellas neutron star mergers.

• We discuss the production of r-process elements in three of these suggested sites:1.the neutrino wind in core collapse supernovae, 2. jet ejecta from magneto-rotationallydriven (MHD) supernovae, and 3. neutron star mergers, with respect to the predicted envi-ronment conditions and the uncertainties in nuclear input physics. This comes to the con-clusion that regular core collapse supernovae cannot be the source of the heaviest r-processelements, there is a slight chance that minor contributions for medium-heavy r-processnuclei originate from them.

• In a second step we utilize Europium (Eu) in old metal-poor stars as the most indicativeelement to trace the r-process production in galactic evolution, since it is dominantly madeby the r-process and relatively easy to observe compared to other heavy r-process elements.We test the most important parameters affecting the chemical evolution of our Galaxy as afunction of metallicity ([Fe/H]) with an inhomogeneous (not automatically mixed) model.These are (a) for neutron star mergers the coalescence time scale of mergers and the probabil-ity to experience such a merger event after two supernova explosions occurred and formeda double neutron star system, and (b) for the sub-class of MHD-supernovae their occurrencerate compared to standard supernovae.

• The main results are the following: The observed [Eu/Fe] pattern in the Galaxy can bereproduced by a combination of neutron star mergers and MHD-supernovae as r-processsources. While neutron star mergers alone seem to set in at too high metallicities, MHD-SNe provide a cure for this deficiency at low metallicities. Furthermore, we confirm thatlocal inhomogeneities can explain the observed large spread in the Eu abundances at lowmetallicities. We also predict the evolution of oxygen ([O/Fe]) as a function of metallicity,to test whether the spread in so-called α-elements for inhomogeneous models agrees withobservations, and whether this provides either constraints on supernova explosion modelsand their nucleosynthesis or clues on mixing processes in the interstellar medium.

Primary author: THIELEMANN, Friedrich (University of Basel)

Co-authors: Mr WEHMEYER, Benjamin (University of Basel); Dr PIGNATARI, Marco (Universityof Basel); Mr EICHLER, Marius (Unibersity of Basel)

Presenter: THIELEMANN, Friedrich (University of Basel)



28th Texas Symp … / Report of Contributions Gravitational waveform from bina …


Gravitational waveform from binary neutron starmergers: Numerical relativity and Effective-one body


Measuring the neutron-star equation of state with gravitational waves is one of the scientificgoal of grand-based gravitational-wave laser interferometers. To achieve this, we need end-to-end waveforms of binary neutron star mergers. Here we present waveforms that are computedwith a long-term numerical relativity simulation. Then the waveforms are compared with thosecomputed with effective one body formalism including the tidal effect. We construct hybrid wave-forms of binary neutron star mergers from 100Hz to 2000Hz. We discuss measurabilities of theequation of state with these hybrid waveforms.

Primary author: HOTOKEZAKA, Kenta (Hebrew University)

Co-authors: KYUTOKU, Koutarou; SHIBATA, Masaru (Kyoto University); Dr SEKIGUCHI, Yuichiro(Toho University)

Presenter: HOTOKEZAKA, Kenta (Hebrew University)



28th Texas Symp … / Report of Contributions ASTRI SST-2M prototype and AST …


ASTRI SST-2M prototype and ASTRI mini-array dataanalysis and scientific prospects in the framework of

the Cherenkov Telescope ArrayWednesday, December 16, 2015 5:00 PM (20 minutes)

In the framework of the international Cherenkov Telescope Array (CTA) observatory, the ItalianNational Institute for Astrophysics (INAF) is developing the ASTRI SST-2M end-to-end prototype,installed at Mt. Etna (Italy) on September 2014, and is leading, in collaboration with Universi-ties from Brazil and South Africa, the ASTRI mini-array composed of nine ASTRI small-sized,dual-mirror telescopes and proposed to be installed at the CTA southern site. The project is alsoincluding the full data handling chain from raw data up to final scientific products, and a dedi-cated software for data reduction and scientific analysis is under development for both the ASTRISST-2M prototype and the ASTRI mini-array, in compliance with the CTA requirements. In thiscontribution, we discuss in detail the outcome of the developed scientific analysis on both ASTRIprototype and mini-array simulated data, in order to provide information on the expected sensi-tivities and to introduce the main scientific prospects for the mini-array.

Collaboration

ASTRI Collaboration and CTA Consortium

Primary author: Dr LOMBARDI, Saverio (OAR-INAF, ASDC)

Co-authors: ASTRI, Collaboration (http://www.brera.inaf.it/astri/); CTA, Consortium (http://www.cta-observatory.org)

Presenter: Dr LOMBARDI, Saverio (OAR-INAF, ASDC)



28th Texas Symp … / Report of Contributions Escape model: CR composition an …


Escape model: CR composition and diffusegamma-ray and neutrino backgrounds


I review the escape model for Galactic cosmic rays (CRs) that reproduce over a wide range ofenergies all available experimental data for individual groups of CR nuclei.Then I discuss how the extragalactic proton component derived within this model can be explainedby astrophysical sources, especially blazars. The diffuse neutrino and γ-ray fluxes produced bythese CR protons interacting with gas inside their sources contribute the dominant fraction ofboth the isotropic γ-ray background and of the extragalactic part of the astrophysical neutrinosignal observed by IceCube.

Primary author: KACHELRIESS, Michael (NTNU)

Presenter: KACHELRIESS, Michael (NTNU)



28th Texas Symp … / Report of Contributions A relativistic approach to large- …


A relativistic approach to large-scale structureMonday, December 14, 2015 2:00 PM (21 minutes)

As high-redshift galaxy surveys probe ever larger volumes with increasing accuracy there is re-newed interest, and some concern, about how the standard results derived within the standardNewtonian approach to large-scale structure should be understood within a relativistic framework.How and when do Newtonian results need to modified? Relativistic corrections arise in severalways. For instance, the nonlinear constraint equations of general relativity impose different non-Gaussian initial conditions on the primordial density field in specific gauges. However we need todefine the spatial and temporal gauge being used in our theoretical models in order to make physi-cal predictions on cosmological scales. As an example, I will show how we may interpret standardN-body simulations most simply as evolution in a specific “N-body gauge”, at least to first order ingeneral relativity. I will also discuss some outstanding issues beyond linear perturbation theory.

Primary author: WANDS, David (University of Portsmouth)

Presenter: WANDS, David (University of Portsmouth)



28th Texas Symp … / Report of Contributions A stiff Higgstory of the Universe


A stiff Higgstory of the UniverseMonday, December 14, 2015 4:35 PM (20 minutes)

I will present the cosmological implications of the decay of the Standard Model Higgs after Infla-tion, when assuming a post-inflationary/pre-BBN expansion history driven by a stiff source withequation of state w > 1/3. In particular, I will discuss first the realisation of a successful ‘reheat-ing’ mechanism, and secondly, the production of a large background of gravitational waves by theHiggs decay products.

Primary author: Dr FIGUEROA, Daniel G. (CERN)

Presenter: Dr FIGUEROA, Daniel G. (CERN)



28th Texas Symp … / Report of Contributions Testing the dark sector interaction …


Testing the dark sector interaction by using theisolated galaxy pairs from SDSS DR10


By analyzing the spin alignment of isolated galaxy pairs from SDSS DR10 and in N-body simulationdata for the coupled dark energy (cDE) model, we constrain the strength of dark sector interactionof cDE model. We perform Kolmogorov-Smirnov 2-sample tests to 6 different cases, one is thespin alignments from SDSS DR10 and in N-body simulation data for LCDM model, others are thespin alignments from SDSS DR10 and in N-body simulation data for cDE models with 5 differentvalues of the strength of dark sector interaction. As a result, LCDM model and cDE model withzero dark sector interaction are the most consistent to SDSS DR10.

Primary authors: Mr KOO, Hanwool (Seoul National University); Prof. LEE, Jounghun (SeoulNational University)

Presenter: Mr KOO, Hanwool (Seoul National University)



28th Texas Symp … / Report of Contributions Presence of a third body orbiting a …


Presence of a third body orbiting around XB1916-053.


The ultra-compact dipping source XB 1916-053 has an orbital period ofclose to 50 min and a companion star with a very low mass (lessthan 0.1 M⊙). The known orbital period derivative(1.5(3)× 10−11 s/s) is extremely large and can beexplained by invoking an extreme, non-conservative mass transferrate that is noteasily justifiable. We extended the analysed datafrom 1978 to 2014, by spanning 37 years, to verify whether alarger sample of data can be fitted with a quadratic term or adifferent scenario has to be considered. The 27 delays associated with the dip arrival times are wellfitted using a sinusoidal term plus a quadratic functionor, alternatively, with a series of sinusoidal terms that can beassociated with a modulation of the dip arrival times due to thepresence of a third body that has an elliptical orbit. We inferthat for a conservative mass transfer scenario the modulation of thedelays can be explained by invoking the presence of a third body withmass between 0.10-0.14 M⊙,orbital period around the X-ray binary system of close to 51 yrand an eccentricity of 0.28± 0.15.In a non-conservative mass transfer scenario we estimate that thefraction of matter yielded by the degenerate companion star andaccreted onto the neutron star is β = 0.08, the neutron starmass is ≥ 2.2 M⊙, and the companion star mass is 0.028 M⊙.In this case, we explain the sinusoidal modulation of the delays byinvoking the presence of a third body with orbital period of 26 yr andmass of 0.055 M⊙. From the analysis of the delays,we find that both in a conservative and non-conservative mass transferscenario we have to invoke the presence of a thirdbody to explain the observed sinusoidal modulation.We propose that XB 1916-053forms a hierarchical triple system.

Primary author: Prof. IARIA, Rosario (Univ. di Palermo - DSFC)

Co-authors: Dr RIGGIO, Alessandro (Univ. di Cagliari); Dr SANNA, Andrea (Univ. di Cagliari); MrGAMBINO, Angelo Francesco (Univ. di Palermo); Mrs SCARANO, Fabiana (Univ. di Cagliari); DrPINTORE, Fabio (Univ. di Cagliari); Prof. BURDERI, Luciano (Univ. di Cagliari); Prof. DI SALVO,Tiziana (Univ. di Palermo - DSFC); Dr MATRANGA, marco (Univ. di Palermo - DSFC)

Presenter: Prof. IARIA, Rosario (Univ. di Palermo - DSFC)


28th Texas Symp … / Report of Contributions Presence of a third body orbiting a …



28th Texas Symp … / Report of Contributions Causality in theories with more th …


Causality in theories with more than one metricMonday, December 14, 2015 4:40 PM (25 minutes)

I will discuss how considerations of causality put constraints on modifications of gravity wherethe perturbations in new degrees of freedom propagate on an acoustic metric different from thespace time metric. More to come.

Primary author: SAWICKI, Ignacy Leonard (University of Geneva)

Co-author: VIKMAN, Alexander

Presenter: SAWICKI, Ignacy Leonard (University of Geneva)



28th Texas Symp … / Report of Contributions Non-local gravity and comparison …


Non-local gravity and comparison withobservational datasets


We study the cosmological predictions of two recently proposed non-local modifications of Gen-eral Relativity. Both models have the same number of parameters asΛCDM, with a mass parameterm replacing the cosmological constant. We implement the cosmological perturbations of the non-local models into a modification of the CLASS Boltzmann code, and we make a full comparison toCMB, BAO and supernova data. We find that the non-local models fit these datasets very well, atthe same level as ΛCDM.For both non-local models parameter estimation using Planck+JLA+BAO data gives a value of H0

slightly higher than in ΛCDM.

Primary author: DIRIAN, Yves (University of Geneva)

Co-authors: KUNZ, Martin (Universite de Geneve (CH)); MAGGIORE, Michele (Universite de Gen-eve (CH)); FOFFA, Stefano (Universite de Geneve (CH)); PETTORINO, Valeria (U)

Presenter: DIRIAN, Yves (University of Geneva)



28th Texas Symp … / Report of Contributions The peculiar X-ray variability of th …


The peculiar X-ray variability of the transitionalpulsar IGR J18245-2452


The pulsar IGR J18245−2452 was dubbed as transitional, after detection of X-ray accretion in-duced pulsations, during an outburst which interrupted radio, rotationally-powered emission. Thesource was observed at the peak of its X-ray flux using XMM-Newton twice for a total exposureof 90 ks. At odds with other accreting millisecond pulsars, its power spectrum is characterisedby a strong flicker noise with no measurable low-frequency cutoff and very weak additional band-limited noise (Ferrigno et al., 2014). The count-rate changes by two orders of magnitudes in timeintervals as short as a few second, and the spectra are luminosity dependent. Moreover thereare episodes of spectral hardening during the lower-flux periods. This might be indicative of theonset of mass ejection from the inner disk boundary with variable intensity, know as weak andstrong propeller. Theoretical and numerical modelling of disk-magnetospheric interaction pre-dicts that when this effect takes place, the accretion-induced luminosity might present transientquasi-periodic behaviour due to the accumulation of matter at the magnetospheric boundary andits subsequent accretion.

In this contribution, we present the rich phenomenology of this still unique object and the simi-larities with other objects of the same class. We will then focus on our search for transient quasi-periodic signals using different techniques such as dynamical power spectra and wavelet analysis.We compare our results with the output of models in which matter is ejected from the disk by theinteraction with the neutron star’s magnetic field and it is partially recycled at an outer radius.This might induce a variable accretion rate responsible of the strong flares and dips in the lightcurve with an apparent stochastic behaviour.

Primary author: FERRIGNO, Carlo (University of Geneva)

Co-authors: PAPITTO, Alessandro; REA, Nanda (CSIC)

Presenter: FERRIGNO, Carlo (University of Geneva)



28th Texas Symp … / Report of Contributions Fitting gamma-ray burst prompt e …


Fitting gamma-ray burst prompt emission spectrawith a model for subphotospheric dissipation


The prompt emission mechanism of gamma-ray bursts (GRBs) is still unknown. While GRB spectraare usually well fitted by the Band function, an empirically motivated, smoothly broken power law,this gives little understanding of the underlying radiation mechanism. In this talk I will present re-sults from fitting a physical model to prompt GRB spectra observed by Fermi. The model simulatesthe scenario of dissipation of kinetic energy below the photosphere in a relativistically expandingfireball. It is based on the code by Pe’er et al. 2005 and includes Compton and Inverse Comptonscattering, synchrotron emission as well as pair production/annihilation. The data are fitted usingan Xspec table model created from a large number of simulations. Our initial results show that themodel can provide good fits to different types of spectra, capturing spectral features not caught bythe corresponding Band function fits. I will present our latest results from fitting the model anddiscuss the implications of our best-fit parameters.

Collaboration

Fermi LAT collaboration

Primary author: AHLGREN, Björn (KTH Royal Institute of Technology)

Co-authors: Dr PE’ER, Asaf (University College Cork); Prof. RYDE, Felix (KTH Royal Institute ofTechnology); Dr LARSSON, Josefin (KTH Royal Institute of Technology); Dr NYMARK, Tanja (KTHRoyal Institute of Technology)

Presenter: AHLGREN, Björn (KTH Royal Institute of Technology)



28th Texas Symp … / Report of Contributions Relativistic tidal disruption events: …


Relativistic tidal disruption events: what do we learnfrom their rate distribution?


We will report on the discovery potential of relativistic tidal disruption events with current andfuture instruments and its impact on the SuperMassive black hole mass function and the theoryof jet formation.Relativistic TDEs (or jetted TDEs) are a new class of sources, recently discovered by Swift/BAT,showing a significant radio counterpart of a common tidal disruption event. Observing relativisticTDEs (from previously non-active galaxies) provides us with a new means of studying the earlyphases of jet formation and evolution in an otherwise pristine environment. Although several(tens) TDEs have been discovered since 1999, only three jetted TDEs have been recently discov-ered in hard X-rays, and two of them, Swift J1644+57 and Swift J2058+05, have a precise localizationwhich further supports the TDE interpretation. We will discuss how the highest discovery poten-tial for relativistic TDEs is not held by current and up-coming X-ray instruments (only a few to afew tens events per year expected) but by the Square Kilometer Array (SKA). We expect SKA todetect TDEs and trigger multi-wavelength follow-ups, yielding hundreds candidates per year evenat high z. Radio and X-ray synergy, however, can in principle constrain important quantities suchas the absolute rate of relativistic TDEs, their jet power, bulk Lorentz factor, the black hole massfunction, and perhaps cover massive black holes with < 10^5 Msun.

Primary author: DONNARUMMA, Immacolata (National Institute for Astrophysics - INAF)

Presenter: DONNARUMMA, Immacolata (National Institute for Astrophysics - INAF)

28th Texas Symp … / Report of Contributions Update on Dark Matter constraints …


Update on Dark Matter constraints from CMBanisotropies


Cosmology, and especially the CMB anisotropies, has been proved to be a powerful tool in thequest for pinning down the nature of Dark Matter (DM).In this talk, I will review how it is possible to get very competitive constraints on the lifetimeand the fraction of unstable DM particles, as well as constraints on the annihilation cross section,using either purely gravitationnial arguments, and/or from the impact of decay products on theanistropies of the CMB.I will present new results using the very last Planck data and comment on perspective on newprobes for testing DM properties with Cosmology.

Primary author: POULIN, Vivian (Unite Reseaux du CNRS (FR))

Co-authors: LESGOURGUES, Julien; SERPICO, Pasquale (Unite Reseaux du CNRS (FR))

Presenter: POULIN, Vivian (Unite Reseaux du CNRS (FR))



28th Texas Symp … / Report of Contributions Multimessenger searches for WIM …


Multimessenger searches for WIMPs withsuppressed interactions


WIMPs with suppressed interactions can present observational challenges at lowest order. Westudy Majorana DM interacting via an axial-vector Z’, where both the self-annihilation rate andWIMP-nucleon scattering rate are suppressed. By including loop diagrams in the calculation ofthe self-annihilation rate, we find that the self-annihilation rate is notably enhanced relative to thetree-level rate, and that the branching ratios to gauge-boson final states become non-negligible. Weshow that the former leads to enhanced constraints on the gamma-ray flux from Fermi and HESS,and the latter leads to stronger constraints on the spin-dependent WIMP-nucleon scattering ratederived from IceCube observations of the neutrino flux from the Sun.

Primary authors: KATZ, Andrey (CERN); RIOTTO, Antonio Walter (Universite de Geneve (CH)); RACCO,Davide (Universite de Geneve (CH)); MORGANTE, Enrico (Universite de Geneve (CH)); RAMEEZ, Mo-hamed (Universite de Geneve (CH)); JACQUES, Thomas David (Universite de Geneve (CH))

Presenter: JACQUES, Thomas David (Universite de Geneve (CH))



28th Texas Symp … / Report of Contributions A loophole to the electromagnetic …


A loophole to the electromagnetic cascade theory :Solving the lithium problem with a sterile neutrino.


After a recap of the standard e.m. cascade theory, I will discuss a loopholethat can have a large effect in the early universe, notably in alteringprimordial nucleosynthesis bounds on electromagnetically decaying relic particles.I will finally show how this may greatly simplify the possibility to addressthe long-standing “lithium problem” in terms of new physics models, and solve it explicitely witha proof-of-principle particle physics model, namely the sterile neutrino.

Primary author: POULIN, Vivian (Unite Reseaux du CNRS (FR))

Co-author: SERPICO, Pasquale (Unite Reseaux du CNRS (FR))

Presenter: POULIN, Vivian (Unite Reseaux du CNRS (FR))



28th Texas Symp … / Report of Contributions A direct measurement of tomogra …


A direct measurement of tomographic lensing powerspectra from CFHTLenS


We measure the weak gravitational lensing shear power spectra and their cross-power in two pho-tometric redshift bins from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). Themeasurements are performed directly in multipole space in terms of adjustable band powers. Forthe extraction of the band powers from the data we have implemented and extended a quadraticestimator, a maximum likelihood method that allows us to readily take into account irregular sur-vey geometries, masks, and varying sampling densities.We find the 68 per cent credible intervals in the σ8–Ωm-plane to be marginally consistent withresults from Planck for a simple five parameter ΛCDM model. For the projected parameterS8 ≡ σ8(Ωm/0.3)0.5 we obtain a best-fitting value of S8 = 0.768+0.045

−0.039. This constraint is con-sistent with results from other CFHTLenS studies as well as the Dark Energy Survey. Our mostconservative model, including modifications to the power spectrum due to baryon feedback andmarginalization over photometric redshift errors, yields an upper limit on the total mass of threedegenerate massive neutrinos of Σmν < 4.53 eV at 95 per cent credibility, while a Bayesianmodel comparison does not favour any model extension beyond a simple five parameter ΛCDMmodel. Combining the shear likelihood with Planck breaks the σ8–Ωm-degeneracy and yieldsσ8 = 0.817+0.013

−0.014 and Ωm = 0.298 ± 0.011 which is fully consistent with results from Planck

alone.

Primary author: KÖHLINGER, Fabian

Co-authors: Dr JOACHIMI, Benjamin (University College London); Dr HOEKSTRA, Henk (LeidenObservatory); Prof. KUIJKEN, Konrad (Leiden Observatory); Dr VIOLA, Massimo (Leiden Observa-tory); VALKENBURG, Wessel (Leiden University)

Presenter: KÖHLINGER, Fabian

28th Texas Symp … / Report of Contributions Recent Developments on X-ray Sig …


Recent Developments on X-ray Signals from DarkMatter Decay in Galaxies and Galaxy Clusters


The latest observational status of the candidate dark matter decay signal at 3.5 keV will be pre-sented. This unidentified X-ray line is observed in multiple galaxies and galaxy clusters. Instru-mental effects or plasma emission are disfavoured while the observations are consistent with adecaying dark matter interpretation. In addition to a review of the existing work, the latest devel-opments will be discussed.

Primary author: FRANSE, Jeroen (Leiden University)

Presenter: FRANSE, Jeroen (Leiden University)



28th Texas Symp … / Report of Contributions Narrow-line Seyfert 1 galaxies - re …


Narrow-line Seyfert 1 galaxies - rebels of the AGNfamilyThursday, December 17, 2015 2:00 PM (20 minutes)

The presence of powerful relativistic jets in narrow-line Seyfert 1 galaxies (NLS1) was confirmedwhen Fermi detected gamma-rays from a handful of them. In the current active galactic nuclei(AGN) paradigm powerful relativistic jets are produced only in massive elliptical galaxies withsupermassive black holes, but NLS1 galaxies challenge this scenario since they have lower blackhole masses, higher accretion rates, preferably compact radio morphology and they reside mostlyin spiral galaxies.

Due to Fermi’s discovery the AGN unification schemes have to be revised to fit in NLS1 galaxies.It also invokes questions about the AGN evolution; what triggers and maintains the AGN activity,and what are the evolutionary lines of the different populations? NLS1 galaxies complicate thewhole AGN scenario, but also offer a new perspective at the jet phenomena.

NLS1 galaxies are a poorly studied class of AGN. It seems that a surprisingly large fraction of themare radio-loud and thus possibly host jets; but also some of them seem to be radio-silent. This, aswell as other observational evidence, implies that they do not form a homogeneous class. However,we are not certain what is the origin of the radio loudness, but, for example, the properties of thehost galaxy and the large-scale environment might play a role.

We used various statistical methods, for example, multifrequency correlations and principal com-ponent analysis to study a large sample of NLS1 sources. Here we present the results and discussthe interplay between their properties, such as emission properties, black hole masses, large-scaleenvironments, and their effect on radio loudness. We also present the first results of the MetsähoviRadio Observatory NLS1 galaxy survey and show some highlights of individual sources.

Primary author: JÄRVELÄ, Emilia (Aalto University Metsähovi Radio Observatory)

Co-author: Prof. LÄHTEENMÄKI, Anne (Aalto University Metsähovi Radio Observatory)

Presenter: JÄRVELÄ, Emilia (Aalto University Metsähovi Radio Observatory)



28th Texas Symp … / Report of Contributions MWL characterization of the blaza …


MWL characterization of the blazar S5 0716+714 byMAGIC during its brightest outburst


S5 0716+714 is a well known BL-Lac object, located at a redshift of z=0.31. The discovery in theVery High Energy band (VHE, E> 100 GeV) by MAGIC happened in 2008, when Fermi data in theHigh Energy (HE, 100 MeV < HE<100 GeV) were not yet available. In January 2015 the sourcewent through the brightest optical state ever observed, triggering MAGIC follow-up and a VHEdetection with ~13 sigma significance (Atel #6999). The availability of simultaneous Fermi-LATobservations allows to constrain the Inverse Compton peak of the spectrum. We will presentthe preliminary analysis of MAGIC data of the flaring activity in January and February 2015 anddiscuss the time variability of the spectrum in VHE during this impressive outburst.Multi Wave Length data including the mm/optical/X-ray/HE bands will be reported. Preliminarystudy on the Extragalactic Background Light absorption willalso be shown, with implications on current EBL models.

Collaboration

MAGIC + Fermi +other MWL authors

Primary author: Dr MANGANARO, Marina (IAC)

Co-authors: Dr RANI, Bindu (Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 D-53121Bonn Germany); GASPARRINI, Dario (ASDC/ INFN Perugia); BASTIERI, Denis (INFN Padova); LIND-FORS, Elina (University of Turku); Dr BORMAN, Geoge (Crimean astrophysical observatory); Dr PED-ALETTI, Giovanna (DESY); BECERRA GONZALEZ, Josefa (NASA GSFC); Dr DOERT, Marlene (TUDortmund); Mr NIEVAS, Miguel (Universidad Complutense, E-28040 Madrid, Spain); Dr JORSTAD,Svetlana (Institute for Astrophysical Research Boston University); Dr LARIONOV, Valeri M. (SobolevAstronomical Inst St Petersburg State Univ Universitetskij pr 28 198504 St Petersburg Russian Federa-tion); FALLAH RAMAZANI, Vandad (University of Turku)

Presenter: Dr MANGANARO, Marina (IAC)

28th Texas Symp … / Report of Contributions Constraining emission mechanism …


Constraining emission mechanisms in gamma-raybursts using spectral width


The emission processes active in the highly relativistic jets of gamma-ray bursts (GRBs) remain un-known. The spectra are usually well-fit by the Band function, an empirically motivated smoothly-broken power law, yet this gives little understandingof the underlying radiation mechanisms. In this talk we propose a new measure to describe spec-tra: the width of the EFE spectrum, a quantity dependent only on finding a good fit to the data.We apply this to the full sample of peak flux GRBspectra observed by CGRO/BATSE combined with the 2nd Fermi/GBM catalog. The results fromthe two instruments are fully consistent. We find that 78% of long GRBs and 85% of short GRBscannot be explained by standard slow cooling synchrotron from a Maxwellian distribution of elec-trons, and almost half the spectra are more narrow that monoenergetic synchrotron. Conversely,photospheric emission can explain the spectra if mechanisms are invoked to give a spectrum muchbroader than a blackbody. We further find that the median widths of spectra from long and shortGRBs are significantlydifferent, and this is thus a new, independent distinction between the two classes. We will discussthe implications of theseresults and the constraints they place on possible emission mechanisms.

Primary author: AXELSSON, Magnus

Co-author: Dr BORGONOVO, Luis (Stockholm University)

Presenter: AXELSSON, Magnus



28th Texas Symp … / Report of Contributions Sterile neutrinos with secret intera …


Sterile neutrinos with secret interactionsTuesday, December 15, 2015 4:36 PM (21 minutes)

The motivation for new non-standard interactions in the sterile neutrino sector arises from the ten-sion between oscillation data and cosmological data, indeed the former point towards the existenceof one (or more) light sterile neutrino in the eV mass range, while the latter disfavor additionalmassive species with high statistical significance. However a partial thermalization induced by se-cret interactions can solve this tension, making eV sterile neutrinos fully consistent with big bangnucleosynthesis, cosmic microwave background and large scale structure measurements.In this talk I will present a pseudoscalar model of secret interactions which provides a simple andelegant way of reconciling eV sterile neutrinos with precision cosmology. I will also mention howthe hidden interactions can be extended to the dark matter sector and might mitigate the smallscale problems of the standard cold dark matter paradigm.

Primary author: ARCHIDIACONO, Maria

Presenter: ARCHIDIACONO, Maria



28th Texas Symp … / Report of Contributions High Energy flares of FSRQs


High Energy flares of FSRQsWednesday, December 16, 2015 2:22 PM (20 minutes)

High-Energy gamma-ray flares (E>10 GeV) of Flat Spectrum Radio Quasars (FSRQ) give us strongconstraints of jet-physics, and of the surrounding-medium.We performed the first study of these flares, examining FERMI-LAT archival-data, and triggering∼40 ToO-observations from near-ir to TeV (e.g., for PKS 1441+25),at the occurrence of new flares.We identified ∼260 gamma-ray flares. Among these, we investigated peculiar and short-flares of3C454.3 and CTA102, showing remarkably hard gamma-ray spectra.We show here the study of a sample of 12 FSRQs, and we discuss the broad-band spectra, andvariability-timescales in terms of injection and cooling of energetic-particles, arguing that theseflares originate at parsec distance from the Supermassive Black-Hole, powered by magnetic-reconnectionsor turbulence in the flow.For the whole sample of 260 flares, we will show spectral and temporal properties, and the corre-lation with disk luminosity during flares.emphasized text

Collaboration

F. Tavecchio, I. Donnarumma, A. Stamerra

Primary author: PACCIANI, Luigi (IAPS/INAF)

Presenter: PACCIANI, Luigi (IAPS/INAF)



28th Texas Symp … / Report of Contributions Signs of magnetic acceleration and …


Signs of magnetic acceleration and multi-zoneemission in GRB 080825C


The era of the Band function paradigm is ending, due in large part to the high-quality data providedby the Fermi Gamma-ray Space Telescope. Practically all bright GRBs detected by Fermi-LAT andGBM data show deviations from a pure Band function, most often due to extra spectral features be-ing present. Understanding the physics of these components is necessary to reveal the accelerationand emission processes active in the highly relativistic outflows of GRBs. Unfortunately, the num-ber of bright GRBs is limited and we therefore look for the presence of possible extra componentsin weaker GRBs, to enlarge the sample. Here we present signs of a new high energy component inGRB080825C. This component is different from those previously reported, and its high energy andtemporal behaviour point to multi-zone emission models where the particle acceleration is due tomagnetic reconnection in the jet.

Collaboration

Fermi-LAT Collaboration

Primary author: MORETTI, Elena (MPI Munich)

Co-author: AXELSSON, Magnus

Presenter: MORETTI, Elena (MPI Munich)



28th Texas Symp … / Report of Contributions Rapid variability as a probe of war …


Rapid variability as a probe of warped space-timearound accreting black holes


The geometry of the inner accretion flow of X-ray binaries is complex, with multiple regions con-tributing to the observed emission. Frequency-resolved spectroscopy is a powerful tool in breakingthis spectral degeneracy. We have extracted the spectra of the strong low-frequency quasi-periodicoscillation (QPO) and its harmonic in GX339-4 and XTE J1550-564, and compare these to the time-averaged spectrum and the spectrum of the rapid (< 0.1s) variability. Our results support thepicture where the QPO arises from vertical (Lense-Thirring) precession of an inhomogeneous hotflow, softer at larger radii closer to the truncated disc and harder in the innermost parts wherethe rapid variability is produced. This coupling between variability and spectra allows us to con-strain the soft Comptonization component, breaking the degeneracy plaguing the time-averagedspectrum and revealing the geometry of the accretion flow close to the black hole.

Primary author: AXELSSON, Magnus

Presenter: AXELSSON, Magnus

28th Texas Symp … / Report of Contributions A bright gamma-ray flare from the …


A bright gamma-ray flare from the blazar B21215+30 detected by VERITAS and Fermi-LAT


We report on evidence of simultaneous gamma-ray flaring from the BL Lac source B2 1215+30,detected by VERITAS (E > 100 GeV) and the Fermi Large Area Telescope (100 MeV < E <100 GeV).The source was observed by VERITAS during an exceptional flaring state in 2014 February 08.Investigations of flux variability in the energy range covered by Fermi-LAT, show that the GeVflare occurred contemporaneously with the TeV flare. From the variability time scale we constrainthe size of the emission region and derive a limit on the Doppler factor of the relativistic jet of B21215+30.

Primary author: ZEFI, Floriana (LLR - Ecole Polytechnique)

Co-authors: Prof. MUKHERJEE, Reshmi (Barnard College, New York); Dr FEGAN, Stephen (LL-R-Ecole Polytechnique)

Presenter: ZEFI, Floriana (LLR - Ecole Polytechnique)

28th Texas Symp … / Report of Contributions Accretion disk around a super- …


Accretion disk around a super-Eddington accretingneutron star


One of the ultraluminous X-ray sources M82 X-2 was recently identified as a neutron star accretingat a rate significantly larger that ordinary X-ray pulsars. The accretion disc outside the magneto-sphere probably still remains below the local Eddington limit but its structure may be affected bythe radiation of the central source (accretion column) that together with magnetic torques shiftsthe centrifugal balance in the inner parts of the accretion disc thus increasing its surface densityand thickness. Magnetosphere radius is also affected by the structure of the disc and may becalculated self-consistently in the framework of our model. We consider the structure of such adisc and corrections to the magnetosphere radius. For large magnetic moments (surface magneticfield ~1013G), the structure of the accretion disc is very close to the standard accretion disc model(Shakura and Sunyaev, 1973), and magnetosphere radius is proportional to the classical Alfvenradius with a constant coefficient. Small magnetic fields, on the other hand, allow the disc to pen-etrate further inside the magnetosphere, but the radius of the magnetosphere becomes relativelylarger with respect to the classic Alfven radius. The inner disc parts in this case show sub-Keplerianrotation (slower by a factor of about 0.75).

Primary author: CHASHKINA, Anna (Tuorla Observatory, University of Turku)

Co-authors: Prof. POUTANEN, Juri (Tuorla Observatory, University of Turku); Mr ABOLMASOV,Pavel (Tuorla Observatory, University of Turku)

Presenter: CHASHKINA, Anna (Tuorla Observatory, University of Turku)



28th Texas Symp … / Report of Contributions Weak lensing mass map in DECaL …


Weak lensing mass map in DECaLS DR1 surveyThursday, December 17, 2015 3:03 PM (21 minutes)

We present the largest weak lensing mass map covering ~3000 square degrees ofthe DECaLS DR1 Survey. A good agreement can be found between optical and dark matter maps.Comparing with the mass maps from CFHT Stripe 82 Survey (CS82), the similar high signal-to-noise ratio peaks can be found, which means the systematics of the maps are well controlled. Wefound ~50,000 WL peaks with SNR higher than 3.0. We also study the cross-correlation betweenWL peaks and massive clusters and galaxies.

Primary author: Dr SHAN, Huanyuan (EPFL)

Presenter: Dr SHAN, Huanyuan (EPFL)



28th Texas Symp … / Report of Contributions A Hamiltonian approach to relativ …


A Hamiltonian approach to relativistic fluiddynamics and binary inspiral


Gravitational waves from neutron-star and black-hole binaries carry valuable information on theirphysical properties and probe physics inaccessible to the laboratory. Neutron stars can be well-modelled as simple barotropic fluids during the part of binary inspiral most relevant to gravita-tional wave astronomy, but the crucial geometric and mathematical consequences of this sim-plification have remained computationally unexploited. In particular, Carter and Lichnerowiczhave described barotropic fluid motion via classical variational principles as conformally geodesic.Moreover, Kelvin’s circulation theorem implies that initially irrotational flows remain irrotational.Applied to numerical relativity, these concepts lead to novel Hamiltonian or Hamilton-Jacobischemes for evolving relativistic fluid flows. Hamiltonian methods can conserve not only flux,but also circulation and symplecticity, and moreover do not require addition of an artificial atmo-sphere typically required by standard conservative methods. These properties can allow produc-tion of high-precision gravitational waveforms at low computational cost.

Primary author: MARKAKIS, Charalampos (University of Southampton)

Presenter: MARKAKIS, Charalampos (University of Southampton)



28th Texas Symp … / Report of Contributions A new view on the Lighthouse Ne …


A new view on the Lighthouse Nebula, IGRJ11014-6103


Despite jets are detected in all kind of accreting systems, bright and elongated jets are known tobe formed also by isolated rotationally powered pulsars.PSR J1101-6101 in the Lighthouse Nebula is an isolated pulsar which is powering a bright windnebula and two jets, while travelling at supersonic velocity in the interstellar medium. Extendingover 15 pc, the jets are more than 10 times longer than the well known Crab pulsar’s jets, and arethe most elongated X-ray jet(s) seen in our Galaxy. Unexpectedly, the jets are perpendicular to thedirection of motion. The wind nebula is tracing the passage of the pulsar in the medium, pointingback to its parent supernova remnant.

The latest data obtained with the Chandra X-ray Observatory give a fresh view on this system.The imaging capabilities of Chandra were used to pinpoint the launching site of the outflows. Thenew data are enlightening spatial and spectral properties of the jets and of the wind nebula.

Primary author: PAVAN, Lucia (University of Geneva)

Co-authors: PUEHLHOFER, Gerd (IAAT); BORDAS, Pol (Max-Planc-Institut fur Kernphysik)

Presenter: PAVAN, Lucia (University of Geneva)



28th Texas Symp … / Report of Contributions Test of relativistic gravity using th …


Test of relativistic gravity using the microlensing ofbroad iron line in quasars


We show that observation of the time-dependent effect of microlensing of relativistically broad-ened emission lines (such as e.g. the Fe Kalpha line in X-rays) in strongly lensed quasars couldprovide data on celestial mechanics of circular orbits in the direct vicinity of the horizon of super-massive black holes. This information can be extracted from the observation of evolution of red /blue edge of the magnified line just before and just after the period of crossing of the innermost sta-ble circular orbit by the microlensing caustic. The functional form of this evolution is insensitiveto numerous astrophysical parameters of the accreting black hole and of the microlensing causticsnetwork system (as opposed to the evolution the full line spectrum). Measurement of the temporalevolution of the red / blue edge could provide a precision measurement of the radial dependenceof the gravitational redshift and of velocity of the circular orbits, down to the innermost stablecircular orbit. These measurements could be used to discriminate between the General Relativityand alternative models of the relativistic gravity in which the dynamics of photons and massivebodies orbiting the gravitating centre is different from that of the geodesics in the Schwarzschildor Kerr space-times.

Primary author: NERONOV, Andrii (University of Geneva)

Co-author: VOVK, Ievgen

Presenter: VOVK, Ievgen



28th Texas Symp … / Report of Contributions Spectral Analysis of ULXs in Pairs …


Spectral Analysis of ULXs in Pairs of InteractingGalaxies M51 and NGC 4485/90 Using Swift-XRT


In this study, we report the examinations of the spectra of ULXs in two nearby (< 10 Mpc) pairs ofinteracting galaxies M51 and NGC 4485/90 collected by Swift-XRT observations from 2005 to 2014and 2008 to 2015 for each target, respectively. We consider 9 ULXs in M51 and 5 ULXs in NGC4485/90. We obtain 116 ObsIDs of M51 and 37 ObsIDs of NGC 4485/90. For each pair of interactinggalaxy, there are about 10% data that do not meet our criteria for further analysis.

The count rate of individual observation ranges from 0.00003 to 0.05 counts/s in 0.3 - 10 keV bandwith typical errorbar ~ 30%. Some ULXs in M51 exhibit a considerable fluctuation of intensity,up to three times, from 0.01 counts/s to 0.03 counts/s. ULXs in NGC 4485/90 show more stablelight curves with no significant changes in intensity. For every source, we divide the data into twocategories, e.g. hard-state (those with hardness ratio ≥ 1) and soft-state (those with hardness ratio <1). Due to the short exposure time during the observation, we got low S/N data with wide errorbar.Therefore, we combine spectrum from many observations with similar spectral characteristics forfitting purpose. We fit the co-added spectra with commonly used models: disk blackbody, powerlaw, and the combination of several models.

Primary author: Ms SULISTIYOWATI, Lis (Institut Teknologi Bandung)

Co-authors: Mr AZIZI, Febrie (Institut Teknologi Bandung); Dr WULANDARI, Hesti (InstitutTeknologi Bandung); Dr VIERDAYANTI, Kiki (Institut Teknologi Bandung); Mr PRIAJANA, Mahadipa(Institut Teknologi Bandung); Dr PREMADI, Premana (Institut Teknologi Bandung)

Presenter: Ms SULISTIYOWATI, Lis (Institut Teknologi Bandung)

28th Texas Symp … / Report of Contributions Simulations of ultralight axion dar …


Simulations of ultralight axion dark matter halosWednesday, December 16, 2015 3:25 PM (20 minutes)

Light scalar fields such as ultra-light axions (ULAs) are dark matter candidates which suppress thegrowth of perturbations on scales below their de Broglie wavelength and predict solitonic halocores owing to their quantum pressure support. They therefore give rise to new phenomenologyin large-scale structure formation and galaxy evolution, including a potential solution to the cusp-core and satellite problems. The nonlinear, non-relativistic dynamics of ULA halos can be describedby the Schroedinger-Poisson equations or, equivalently, the fluid equations with an additionalpressure term. Several approaches to simulate structure formation with ULA dark matter andsome preliminary results will be presented.

Primary author: NIEMEYER, Jens (Goettingen University)

Presenter: NIEMEYER, Jens (Goettingen University)



28th Texas Symp … / Report of Contributions MHD Shocks in Accretion onto a R …


MHD Shocks in Accretion onto a Rotating Black HoleWednesday, December 16, 2015 3:33 PM (3 minutes)

The formation of standing magnetohydrodynamical (MHD) shocks by accreting plasma in a blackhole magnetosphere is studied. The black hole magnetosphere would be formed around a blackhole with an accretion disk. The global magnetic field lines would be originated by currents in theaccretion disk and its corona, and then some part of magnetic field lines would lead to the eventhorizon. Along such magnetic field lines magnetized plasma streams from the disk surface to thehorizon, and on the way to the horizon MHD shock can be generated. Although the postshockplasma becomes very hot, the MHD shock can be expected as a source of high-energy radiation,which is generated very close to the horizon and then carry to us a lot of information of theblack hole spacetime. We also discuss the huge energy release at the MHD shock front, where theplasma’s kinetic energy and the black hole’s rotational energy can convert to radiative energy byconsidering negative energy postshock MHD flows (Takahahi & Takahashi 2010). This means thatthe Blandford-Znajek (1977) power can convert to radiative energy at the MHD shock generatedvery close to the horizon.

Primary author: TAKAHASHI, Masaaki (AIchi University of Education)

Presenter: TAKAHASHI, Masaaki (AIchi University of Education)



28th Texas Symp … / Report of Contributions Origin of the gamma-ray emission …


Origin of the gamma-ray emission from the GalacticCentreThursday, December 17, 2015 3:24 PM (21 minutes)

The Galactic centre (GC) is a bright gamma-ray source with the GeV-TeV band spectrum composedof two distinct components in the 1-10 GeV and 1-10 TeV energy ranges. The nature of these twocomponents is not clearly understood. We present imaging, spectral, and timing analysis of datafrom ~7 years of observations of the Galactic centre by FERMI/LAT gamma-ray telescope comple-mented by sub-MeV data from approximately ten years of INTEGRAL/PICsIT observations. Wediscuss the implications of our observations for the hadronic and leptonic models of the emissionfrom the GC. We also discuss the spatial morphology of the GC in GeV band and compare ourresults with the GeV dark matter excess claims.

Primary author: MALYSHEV, Denys (University of Geneva)

Co-authors: NERONOV, Andrii (University of Geneva); CHERNYAKOVA, Maria (DCU); WALTER,Roland (University of Geneva)

Presenter: MALYSHEV, Denys (University of Geneva)



28th Texas Symp … / Report of Contributions Numerical Models For Superfluid …


Numerical Models For Superfluid Neutron StarsWith Realistic Equation Of State And Application To

Pulsar GlitchesTuesday, December 15, 2015 2:00 PM (21 minutes)

We present a realistic numerical model for rotating superfluid neutron stars in a full general rel-ativistic framework. Following the work initiated by Prix, Novak & Comer [1], we compute sta-tionary axisymmetric configurations of neutron stars composed of two fluids, namely superfluidneutrons and charged particles (protons and electrons), which are free to rotate around a commonaxis with different rigid rotation rates. This system is described by a realistic equation of statederived from a relativistic mean field theory using DDH parametrization including (or not) deltamesons. Then, we apply this model to investigate pulsar glitches in a very simple way. From aseries of equilibrium states of a neutron star, assuming total baryon mass and total angular momen-tum to be constant, we compute the evolution in time of the properties of the star during a glitch.To do so, we model a glitch as a transfer of angular momentum from one fluid to the other, throughthe action of mutual friction force [2]. This enables us to infer characteristic features relative toglitches, such as rise timescales, which could be compared to future accurate observations.

[1] Prix, R., Novak, J. & Comer, G. L., Relativistic numerical models for stationary superfluid neu-tron stars, Phys. Rev. D 71, 2005

[2] Langlois, D., Sedrakian, D. M. & Carter, B., Differential rotation of relativistic superfluid inneutron stars, MNRAS 297, 1998

Collaboration

Sourie, Aurélien; Oertel, Micaela; Novak, Jérôme

Primary author: SOURIE, Aurélien (LUTH - Observatoire de Paris)

Presenter: SOURIE, Aurélien (LUTH - Observatoire de Paris)



28th Texas Symp … / Report of Contributions Theoretical uncertainties in extrac …


Theoretical uncertainties in extracting cosmic raydiffusion parameters: the boron to carbon ratio


PAMELA and, more recently, AMS-02, are ushering us into a new era of greatly reduced statis-tical uncertainties in experimental measurements of cosmic ray fluxes. In particular, new deter-minations of traditional diagnostic tools such as the boron to carbon ratio (B/C) are expected tosignificantly reduce errors on cosmic-ray diffusion parameters, with important implications for as-troparticle physics, ranging from inferring primary source spectra to indirect dark matter searches.It is timely to stress, however, that the conclusions inferred crucially depend on the framework inwhich the data are interpreted as well as from some nuclear input parameters. We aim at assessingthe theoretical uncertainties affecting the outcome, with models as simple as possible while stillretaining the key dependences.We compare different semi-analytical, two-zone model descriptions of cosmic ray transport in theGalaxy: infinite slab/1D, cylindrical symmetry/2D with homogeneous sources, cylindrical symme-try/2D with inhomogeneous source distribution. We test for the effect of a primary source con-tamination in the boron flux by parametrically altering its flux, as well as for nuclear cross-sectionuncertainties. All hypotheses are compared via χ2 minimization techniques to preliminary resultsfrom AMS-02.We find that the major theoretical bias on the determination of the diffusion coefficient index δ

(up to a factor two) is represented by the assumption that no injection of Boron takes place at thesource. The next most important uncertainty is represented by cross-section uncertainties, whichreach ±20% in δ. As a comparison, nuclear uncertainties are more important than the shift in thebest-fit when introducing a convective wind of velocity >30 km/s, with respect to a pure diffusivebaseline model. Perhaps surprisingly, homogeneous 1D vs. 2D performances are comparable indetermining diffusion parameters. An inhomogeneous source distribution marginally alters thecentral value of the diffusion coefficient normalization (at the 10%, 1σ level). However, the indexof the diffusion coefficient δ is basically unaltered, as well as the goodness of fit.Our study suggests that, differently for instance from leptonic case, realistic modeling of the geom-etry of the Galaxy and of the source distribution are of minor importance to correctly reproduceB/C data at high-energies hence, to a large extent, for the extraction of diffusion parameters.The Ansatz on the lack of primary injection of Boron represents the most serious bias, and requiresmulti-messenger studies to be addressed. If that uncertainty could be lifted, nuclear uncertaintieswould still represent a serious concern, which degrade the systematic error on the inferred param-eters to the 20\% level, or three times the estimated experimental sensitivity. In order to reducethis, a new nuclear cross-section measurement campaign is probably required.

Primary author: GENOLINI, yoann (LAPTh)

Co-authors: PUTZE, Antje (Centre National de la Recherche Scientifique (FR)); SALATI, PIERRE(LAPTh & Université de Savoie Mont Blanc); SERPICO, Pasquale (Unite Reseaux du CNRS (FR))

Presenter: GENOLINI, yoann (LAPTh)



28th Texas Symp … / Report of Contributions The shape of a pulsar radio beam: …


The shape of a pulsar radio beam: fan beams, not thenested cones.


The knowledge of radio emission geometry is crucialfor interpreting their gamma-ray profiles, and forestablishing the orientation of their tilted magnetic field.I will review the continually increasing evidence against the most popular (nested cone) radiobeam geometry.It will be shown that several features of pulse profiles,which have normally been considered as signatures of the nested cones,can in fact be readily interpreted through a system of fan beams.These include some properties of the radius-to-frequency mappingas well as the special-relativistic lag of the core component inmulticomponent profiles.A new statistical probe of beam shape will be introduced,based on the ratio of component separationsobserved in M and Q profiles. This method is independent of the parametersthat determine the scale of the beam (emission altitude, frequency,rotation period, dipole tilt) while it retains the sensitivity to thebeam shape. When applied to the Q and M pulse profiles,the method reinforces the problems of the conal geometry and favoursthe azimuthally-structured beam (a system of fan beams).The non-conal geometry has consequences for the gamma-ray profile modelling.

Collaboration

B. Rudak, M. Pierbattista, L. Saha

Primary author: Dr DYKS, Jaroslaw (Nicolaus Copernicus Astronomical Center)

Presenter: Dr DYKS, Jaroslaw (Nicolaus Copernicus Astronomical Center)



28th Texas Symp … / Report of Contributions The effective number of neutrinos: …


The effective number of neutrinos: standard andnon-standard calculations


We have performed a new numerical calculation of the decoupling process of neutrinos in the earlyUniverse, including the values of all mixing parameters from a recent analysis, taking into accountthe full set of differential equations for the neutrino density matrices (equivalent to the occupationnumbers for mixed neutrinos). Our results are important for fixing the radiation content of theUniverse in the standard case in terms of Neff, recently measured by Planck. We also show to whichextent the value of Neff can be enhanced in the presence of non-standard neutrino interactionswith electrons, and we have also considered the case of a very low reheating scenario, where thelast radiation-dominated phase of the Universe begins at temperatures as low as MeV. The mainconsequence of such scenarios concerns the production of neutrinos, because they are the knownrelativistic particles with the largest decoupling temperature. The thermalization of the neutrinobackground could be incomplete due to the lack of interactions, leading to Neff < 3. We willshow the bounds on the reheating temperature both from BBN and from late-time cosmologicalobservables, including the latest results of the Planck satellite.

Primary author: FERNÁNDEZ DE SALAS, Pablo (IFIC - CSIC/Universidad de Valencia)

Co-author: Prof. PASTOR CARPI, Sergio (IFIC - CSIC/Universidad de Valencia)

Presenter: FERNÁNDEZ DE SALAS, Pablo (IFIC - CSIC/Universidad de Valencia)

28th Texas Symp … / Report of Contributions Probing the Extragalactic Backgro …


Probing the Extragalactic Background Light withVERITAS


The observed spectra of active galactic nuclei carry the imprint of gamma-ray interactions withthe extragalactic background light (EBL). As gamma rays from an extragalactic source travel to theobserver, pair production on the EBL plays a role in reprocessing the photons to lower energies, ob-scuring the intrinsic source spectrum. VERITAS, a ground-based imaging atmospheric-Cherenkovtelescope array sensitive to gamma rays above 85 GeV, has collected a large set of observations ofblazars for a range of redshifts. We present the latest VERITAS results from using blazar spectralmeasurements to constrain the EBL’s spectral energy distribution.

Collaboration

VERITAS

Primary author: PUESCHEL, Elisa Kay (University College Dublin)

Presenter: PUESCHEL, Elisa Kay (University College Dublin)



28th Texas Symp … / Report of Contributions Probing the Intergalactic Magnetic …


Probing the Intergalactic Magnetic Fields by meansof high-energy pair halos around extreme blazars


The origin of cosmic magnetic fields permeating galaxies and clusters is still unknown.To undert-stand the origin and the evolution of the primordial cosmic magnetic fields we need to probe theexistence and to characterize magnitude and correlation length of magnetic field in voids (Inter-galactic magnetic field, IGMF), where pollution from magnetic fields associated to structures isexpected to be minimal. Techniques like Faraday Rotation and Zeeman splitting permit to com-pute upper limits on IGMF of the order of 10^-9 G. Nevertheless our knowledge on IGMF is stillpoor.Very High Energy (VHE) photons (E>50 GeV) coming from extreme Blazars interact with Opti-cal/Infrared Extragalactic Background Light (EBL). Because of these interactions electron-positronpairs are produced. These, in turn, upscatter via inverse Compton the CMB photons producing areprocessed emission. If the primary photons have energies higher than 10 TeV this componentwill be in the GeV domain. IGMF deflects the pairs so this component will be in the form of ex-tended emission whose angular extension depends on the strength of IGMF. The detection of thiscomponent is an unique tool to measure the IGMF.The measurement of halo emission by Cherenkov telescopes like MAGIC depends strictly on itscapability to disentangle the extended from the point-like emission of the source. For the first timethe detailed characterization of the PSF of MAGIC has allowed to assess the possibility to revealthe extended emission due to IGMF. We first found a good analytical model for the MAGIC PSFand then, comparing the emission profiles of several AGN with the PSF reference, we obtained thatall souces are point like. Using two different halo emission models we computed for all sourcesupper limits on extended emission. For the source Markarian 421 our procedure provided an upperlimit which is more than three times better than a previous published measurement. In additionwe found that the sources 1ES 0229+200 and RX J1136.5+6737 though well described by a point-source profile, do not exclude the presence of extended emission. In this case the implied strenghtsof IGMF are of the order of 10^-14 G.

Collaboration

MAGIC Collaboration

Primary authors: STAMERRA, Antonio (INAF-OATo / SNS-Pisa); DA VELA, PAOLO (INFN -National Institute for Nuclear Physics)

Co-authors: PRANDINI, Elisa (University of Geneva); VOVK, Ievgen (Max Planck Institute forPhysics); SITAREK, Julian (University of Łódź); KONNO, Yusuke (Kyoto University)

Presenter: DA VELA, PAOLO (INFN - National Institute for Nuclear Physics)



28th Texas Symp … / Report of Contributions Black Holes, Neutron Stars and W …


Black Holes, Neutron Stars and White DwarfCandidates from Microlensing with OGLE-III


Most stellar remnants so far have been found in binary systems where they interact with matterfrom their companion. Isolated neutron stars and black holes are hard to find as they do not emitlight, yet they are predicted to be present in our Galaxy in vast numbers.

We explored the OGLE-III database of 150 million objects observed in years 2001-2009 and found59 microlensing events exhibiting parallax effect due to Earth’s motion around the Sun. Combin-ing parallax and brightness measurements from microlensing light curves with expected propermotions in the Milky Way, we identify 15 microlensing events which are consistent with havinga white dwarf, neutron star or a black hole lens and we estimate their masses and distances. Thedistribution of masses of our candidates indicates a continuum in mass distribution with no massgap. We also present predictions on how such events will be observed by the astrometric Gaiamission.

Primary author: Dr WYRZYKOWSKI, Lukasz (Warsaw University Astronomical Observatory)

Co-author: Dr KOSTRZEWA-RUTKOWSKA, Zuzanna (Warsaw University Astronomical Observa-tory)

Presenter: Dr KOSTRZEWA-RUTKOWSKA, Zuzanna (Warsaw University Astronomical Observa-tory)



28th Texas Symp … / Report of Contributions Dark matter searches with antideu …


Dark matter searches with antideuteronsWednesday, December 16, 2015 5:30 PM (20 minutes)

Antideuterons can be produced through the nuclear coalescence of the antiprotons and the antineu-trons that are originated in a dark matter pair annihilation or decay event. At low kinetic energies,the fluxes of these bound states are found to dominate over the astrophysical background and thusantideuterons may be considered as a very promising channel for a dark matter indirect detection,especially for WIMPs with a low or intermediate mass. In this talk, an overview on the principalissues related both to the antideuterons production and to their subsequent propagation throughthe interstellar medium and the heliosphere will be given. Then, the capability of current andfuture experiments to detect an antideuteron flux produced by dark matter annihilation will beinvestigated in relation to the constraints on the dark matter annihilation cross section that canbe derived from the latest measurements of the cosmic antiproton flux.

Primary author: VITTINO, Andrea (Universita’ di Torino and INFN Torino)

Presenter: VITTINO, Andrea (Universita’ di Torino and INFN Torino)



28th Texas Symp … / Report of Contributions Structure of magnetized transonic …


Structure of magnetized transonic accretion disksThursday, December 17, 2015 5:18 PM (20 minutes)

Using general relativistic analytical treatment in Kerr metric and numerical simulations with thepublic HARM2D code, we consider the vertical structure and velocity field in the inner parts of ablack hole accretion disk, both outside and inside the last stable orbit.

Chaotic magnetic fields frozen into the accreting matter easily become the dominant pressuresource inside the sonic point that allows to predict the equilibrium thickness of the flow. Numericalsimulations, however, reveal instabilities in the magnetic fields leading to formation of currentsheets in the super-sonic part of the flow and ultimately to accretion through thin layers (or wisps,in 3D) with the vertical spatial scale much smaller.

If disk thickness is large, any consideration of its vertical structure should use some assumptionsabout the rotation velocity field inside the disk. The latter seems to be strongly dependent upon thepresence of a regular magnetic field component near the black hole. If the magnetic flux throughthe black hole horizon is small, rotation close to the sonic surface conforms very well to Keple-rian, and isorotational surfaces have practically cylindrical shapes (r sin θ = const). We use theassumption of Keplerian cylindrical rotation Ω(r, θ) =

((r sin θ)3/2 + a

)−1 to estimate the effectsof disk thickness upon the Eddington limit and accretion efficiency in black hole accretion disks.

Primary author: ABOLMASOV, Pavel (University of Turku)

Co-author: CHASHKINA, Anna

Presenter: ABOLMASOV, Pavel (University of Turku)



28th Texas Symp … / Report of Contributions Using Atom Interferometry to Det …


Using Atom Interferometry to Detect ChameleonDark Energy


I will discuss the prospect that the first evidence for dark energy may be found through meter scale,laboratory based, atom interferometry experiments. I will discuss how, in order to be compatiblewith fifth force constraints, dark energy scalar fields must have a screening mechanism whichhides their effects from us within the solar system. Focusing in particular on one such screeningmechanism, known as the chameleon, where the field’s mass becomes dependent on the environ-ment I will show how the field behaves in the presence of a spherical source. In the presence ofthe kind of high vacuum associated with atom interferometry experiments, and when the test par-ticle is an atom, it is possible to use the associated interference pattern to place constraints on theacceleration due to the fifth force of the chameleon field - this has already been used to rule outlarge regions of the chameleon parameter space and may one day be able to detect the force dueto the dark energy field in the laboratory.

Primary author: BURRAGE, Clare (University of Nottingham)

Presenter: BURRAGE, Clare (University of Nottingham)



28th Texas Symp … / Report of Contributions Gravitational waves in a bigravity …


Gravitational waves in a bigravity model: frominflation to present


In this talk, a detailed analysis of the evolution of tensor perturbations in a cosmological back-ground for a model of Hassan-Rosen theory of bigravity is presented. It is shown that gravitationalwaves are unstable in this setting, but also that in practice the amplitude of tensor perturbationsgenerated during inflation is sufficiently suppressed to avoid this instability from showing up untiltoday. Hence, this bigravity model cannot be excluded from a pure analysis of the tensor sector.However, stringent limits on inflation from vector and scalar perturbations are derived.

Primary author: GUARATO, Pietro (Université de Genève)

Co-authors: CUSIN, Giulia (University of Geneva); MOTTA, Mariele (University of Geneva); DUR-RER, Ruth (University of Geneva)

Presenter: GUARATO, Pietro (Université de Genève)



28th Texas Symp … / Report of Contributions Gravitational Wave Signals from 3 …


Gravitational Wave Signals from 3D NeutrinoSimulations of Core-Collapse Supernovae

HydrodynamicsWednesday, December 16, 2015 6:15 PM (20 minutes)

To this day the exact nature of the detonation mechanise in core collapse supernovae remindssomewhat of a mystery. While numerical models are becoming more and more sophisticated,observations of the inner engine remain elusive. Because he core surrounded by dens stellar mat-ter, electromagnetic radiation can only provide indirect information. Neutrinos and gravitationalwaves on the other hand can propagate almost unhindered thought the stellar material. For thelast decade, or so, supernova modellers have predicted gravitational wave signatures based ontheir simulations.

I will follow in these footsteps and present a detailed analysis of the gravitational wave signalduring the post-bounce phase, from the latest core collapse simulations. I present the signal arisingfrom sophisticated three-dimensional simulations of three progenitors.

The theoretical signal from our simulations consists of two distinct features: One emission compo-nent below 250 Hz associated with the standing accretion shock instability and a one componentabove 300 Hz associated mainly with convection deep within the forming neutron star. The formercomponent arises from both the proto-neutron star exterior and interior.

Primary author: ANDRESEN, Haakon (Max Planck Institut für Astrophysik)

Presenter: ANDRESEN, Haakon (Max Planck Institut für Astrophysik)



28th Texas Symp … / Report of Contributions 3D Quantum Bubble Collisions


3D Quantum Bubble CollisionsMonday, December 14, 2015 3:03 PM (21 minutes)

First-order phase transitions proceed through the nucleation and subsequent collision of bubbles.In false vacuum eternal inflation, such collision events are ubiquitous and provide a possible avenueto observationally test the multiverse. They also play an important role in early high temperaturephase transitions.

I will present results for the full three-dimensional nonlinear dynamics of pairwise bubble colli-sions, including for the first time the effects of (initially small) quantum fluctuations. This signif-icantly extends the standard treatment of bubble collisions. In the standard approach, the fieldprofile is assumed to possess a spatial SO(2,1) symmetry and the dynamics reduces to one spatialdimension. However, quantum fluctuations break the assumed symmetry and cannot be studied inthe symmetry based formalism. I will show that accounting for the dynamics of these fluctuationsleads to a complete breakdown of the SO(2,1) symmetry in a wide class of potentials. Initially, thefluctuations experience a linear parametric instability, which can be interpreted as an inhomoge-neous version of Bogoliubov particle production. At the onset of mode-mode coupling, the bubblewalls in the collision region dissolve, leaving behind a population of localized oscillating blobs offield known as oscillons. This has implications for the production of gravitational waves or blackholes during bubble collisions.

Primary author: BRADEN, Jonathan (University College London)

Co-authors: Prof. BOND, J. Richard (CITA); Prof. MERSINI-HOUGHTON, Laura (UNC-ChapelHill)

Presenter: BRADEN, Jonathan (University College London)



28th Texas Symp … / Report of Contributions Dark matter decay and cosmic reio …


Dark matter decay and cosmic reionizationMonday, December 14, 2015 4:15 PM (20 minutes)

We study the impact of dark matter decay on cosmic reionization. We derive new constraintson the dark matter decay rate by using the newest CMB observations, assuming two differentparametrizations of standard reionization.

Primary author: Ms OLDENGOTT, Isabel (Universität Bielefeld)

Presenter: Ms OLDENGOTT, Isabel (Universität Bielefeld)



28th Texas Symp … / Report of Contributions NuSTAR Discovery of Galactic Ce …


NuSTAR Discovery of Galactic Center Hard X-rayEmission


The Galactic Center region contains one of the highest concentration of X-ray sources in the MilkyWay. Recently NuSTAR, with its sub-arcminute spatial resolution, has discovered an unresolvedhard (20-40 keV) X-ray emission within the central 10 pc. This emission is consistent with ei-ther stellar origins, such as large populations of intermediate polars, low-mass X-ray binaries, ormillisecond pulsars, or diffuse origins, such as cosmic-ray outows from the supermassive blackhole Sagittarius A*. However, each of these explanations implies source properties peculiar tothis central region. In particular, the implied average white dwarf mass for the intermediate polarpopulation is > 0.8M⊙. The relation of this population to the much lighter ∼ 0.5M⊙ populationimplied by previous Chandra and XMM-Newton measurements of the surrounding ∼ 50 pc, or tothe ∼ 0.5-0.8M⊙ populations implied by previous Galactic bulge and ridge, nearby field, or SDSSsurvey measurements, is unclear. We present in this contribution details of the central hard X-raydiscovery, as well as follow-up work on a possible intermediate polar interpretation. Using thebroad-band (3-79 keV) energy resolution of NuSTAR and observations of the intermediate polarsTV Columbae and IGR J17303-2601, we argue that both the broad-band NuSTAR measurement ofthe central 10 pc and the low-energy measurements of the surrounding ∼ 50 pc could be attributedto a single population of intermediate polars with mean white dwarf mass ∼ 0.85M⊙.

Collaboration

The NuSTAR Collaboration

Primary author: PEREZ, Kerstin

Presenter: PEREZ, Kerstin



28th Texas Symp … / Report of Contributions Gravitational waves from a therm …


Gravitational waves from a thermal first order phasetransition: numerical simulations


We present large-scale numerical simulations of the gravitational radiation produced by a firstorder thermal phase transition in the early universe. The dominant source of gravitational wavesis sound waves generated by the expanding bubbles of the low-temperature phase. The resultinggravitational wave power spectrum has a power-law form between scales set by the average bubbleseparation and the bubble wall width. However, the general form of the power spectrum is differentfrom that predicted by the widely-applied envelope approximation, and the predicted gravitationalwave energy density is at least two orders of magnitude larger.

Primary author: WEIR, David (University of Stavanger)

Presenter: WEIR, David (University of Stavanger)



28th Texas Symp … / Report of Contributions Supercluster straightness as a cos …


Supercluster straightness as a cosmological testMonday, December 14, 2015 6:15 PM (3 minutes)

We present how an anisotropic pattern of the cosmic web, which is vividly reflected in the filamen-tary structure of supercluster, changes if 1)the nature of dark energy differs from the cosmologicalconstant or 2)the gravitational law deviates from the general theory of relativity with/withoutmassive neutrinos. 1)The coupled dark energy (cDE) model where the coupling between dark en-ergy and dark matter exists and 2)the f(R) gravity model which substitutes Ricci scalar R withfunction f(R) in the Einstein-Hilbert action with\without massive neutrinos are considered for theformer and latter cases, respectively. Since the anisotropy of the clustering of galaxy clusters isrepresented in the degree of straightness of the supercluster, we calculate spine specific size ofthe supercluster as a measure of its straightness using the halo catalogs of N-body simulations forrespective cosmologies at various epochs. It is found that both the cDE and f(R) gravity modelshave the effect of significantly bending the superclusters resulting in the smaller mean values ofthe spine specific sizes compared to that of the ΛCDM, whereas the massive neutrinos contributeto straightening the superclusters. Although the f(R) gravity with the massive neutrinos of thespecific total neutrino mass is hard to discriminate from the ΛCDM since the effect of the f(R)gravity on the supercluster straightness is suppressed at the current epoch, its mean specific sizedeviates significantly from the value of the standard cosmology in higher redshifts (z≥0.3). On thegrounds that the difference in the degree of the supercluster straightness of cDE (f(R) gravity) fromthe ΛCDM increases (decreases) with redshift, the supercluster straightness should play a role ofpowerful cosmological test. A physical interpretation of our results as well as their cosmologicalimplications are discussed.

Collaboration

Jounghun Lee, Baojiu Li, Marco Baldi

Primary author: Mr SHIM, Junsup (Seoul National University)

Co-authors: Dr LI, Baojiu (Durham University United Kingdom); Prof. LEE, Jounghun (SeoulNational University); Dr BALDI, Marco (University of Bologna)

Presenter: Mr SHIM, Junsup (Seoul National University)



28th Texas Symp … / Report of Contributions Search for lensed QSOs in the OG …


Search for lensed QSOs in the OGLE surveyThursday, December 17, 2015 2:42 PM (21 minutes)

We present the results of our search for gravitationally lensed quasars in the OGLE survey. Weshow candidates from a 650 square degrees area behind the Magellanic Clouds System. The studyof strong lensing time delays serves as a powerful probe in cosmology. The OGLE database pro-vides long time light curves, allowing for a cost-effective way to accurately derive time delays andtherefore study Hubble constant.

Primary author: Dr KOSTRZEWA-RUTKOWSKA, Zuzanna

Co-authors: Dr WYRZYKOWSKI, Lukasz (Warsaw University Astronomical Observatory); Dr KO-ZLOWSKI, Szymon (Warsaw University Astronomical Observatory)

Presenter: Dr KOSTRZEWA-RUTKOWSKA, Zuzanna



28th Texas Symp … / Report of Contributions Implications of the primordial pow …


Implications of the primordial power asymmetry forinflation


It is both remarkable, and disappointing, that only two parameters describing the primordial per-turbations can explain the statistical properties of millions of CMB temperature perturbations.However, the persistence of several large-scale cosmological anomalies in WMAP and Planck satel-lite data may provide a clue to new physics. I will discuss how inflationary models can explain theobserved dipolar power asymmetry, and the extreme difficulties of building a complete workingmodel.

Primary author: BYRNES, Christian (University of Sussex (GB))

Presenter: BYRNES, Christian (University of Sussex (GB))



28th Texas Symp … / Report of Contributions THE YOUNG, RELATIVISTIC BIN …


THE YOUNG, RELATIVISTIC BINARY PULSARJ1906+0746


PSR J1906+0746 is a young pulsar in the relativistic binary with the second-shortest known orbit, of3.98 hours. We will present a timing study based on five years of observations, conducted with the5 largest radio telescopes in the world, aimed at determining the companion nature (van Leeuwenet al. 2015). Through the measurement of three post-Keplerian orbital parameters we find thepulsar and companion masses to be 1.323(11)M and 1.290(11)M respectively. These masses arecompatible with a neutron star companion, but also fit well in the known mass distribution ofwhite dwarfs around young pulsars such as J1906+0746. Neither radio pulsations nor anydispersion-inducing outflows that could have established the companion nature were detected.We derive an HI-absorption distance, which indicates an optical confirmation of a white dwarfcompanion is very challenging. The pulsar is fading fast due to geodetic precession, limiting futuretiming improvements. We conclude that young pulsar J1906+0746 is either part of a binary neutronstar, or is orbited by an older white dwarf, in an exotic system formed through two stages of masstransfer.

Primary author: VAN LEEUWEN, Joeri (ASTRON / U. Amsterdam)

Co-author: STAIRS, Ingrid (UBC)

Presenter: VAN LEEUWEN, Joeri (ASTRON / U. Amsterdam)



28th Texas Symp … / Report of Contributions The first detection of the blazar S4 …


The first detection of the blazar S4 0954+65 atvery-high energies with the MAGIC Telescopes

during an exceptionally high optical stateTuesday, December 15, 2015 5:15 PM (20 minutes)

The blazar S4 0954+65 (at a redshift of z=0.368) underwent an exceptionally high state in opticalduring January and February 2015, as revealed by the Tuorla and St.Petersburg University blazarmonitoring programs: a brightening of more than 3 magnitudes in the R-band from the averagemonitored states. Simultaneous data from the Fermi-LAT satellite at high energy gamma rays(100MeV < E < 100GeV) also show a period of increased activity.

MAGIC observations, triggered by these enhanced emissions in lower energy bands, led to thediscovery of very high energy (VHE, E>100 GeV) emission from S4 0954+65 (ATel #7080). The VHEflux above 150GeV is estimated to be about 6% of the Crab nebula flux above the same threshold.

In this contribution we present a comprehensive multiwavelength picture of this object, includingdata from mm/optical/X-ray/HE and VHE gamma-ray bands along with analysis of the parsec scalejet behavior.

Collaboration

MAGIC

Primary author: PEDALETTI, Giovanna (DESY)

Co-authors: MARSCHER, Alan (Institute for Astrophysical Research Boston university); GEORGE,Borman (Crimean astrophysical observatory); LINDFORS, Elina (University of Turku); TROITSKY, Ivan(Astronomical Institute of St.Petersburg University); BECERRA GONZALEZ, Josefa (NASA GSFC); MAN-GANARO, Marina (IAC); DOERT, Marlene (TU Dortmund); NIEVAS ROSILLO, Miguel (UCM); JORSTAD,Svetlana (Institute for Astrophysical Research Boston university); LARIONOV, Valeri (Astronomical In-stitute of St.Petersburg University); FALLAH RAMAZANI, Vandad (University of Turku)

Presenter: PEDALETTI, Giovanna (DESY)

28th Texas Symp … / Report of Contributions Acoustically generated gravitation …


Acoustically generated gravitational waves fromthermal first order phase transitions


Recent numerical simulations have demonstrated that the most important source of gravitationalradiation from a thermal first order phase transition in the early Universe is the sound wavesit produces. I outline the theory of the acoustic production of gravitational waves from phasetransitions, showing how both the amplitude and shape of the power spectrum can be simplyunderstood. Implications for the detectability of a first-order electroweak transition by futurespace-based detectors will be briefly discussed.

Primary author: HINDMARSH, Mark (University of Sussex)

Co-authors: WEIR, David (University of Stavanger); RUMMUKAINEN, Kari (University of Helsinki); MsHOPKINS, Nicola (University of Sussex); HUBER, Stephan (Unknown)

Presenter: HINDMARSH, Mark (University of Sussex)



28th Texas Symp … / Report of Contributions Linear perturbations in massive bi …


Linear perturbations in massive bigravity:formalism and cosmology


In this talk I will discuss linear perturbations of dRGT massive bi-gravity with a single metriccoupled to matter. First, I will introduce the formal derivation of the second order action forgeneric metrics. I will then use this result to identify stability bounds. Finally, I will discuss thelinear perturbations on a FRW background, the cosmology of different branches, the number ofdegrees of freedom of the theory and the presence of instabilities.

Primary author: MOTTA, Mariele (University of Geneva)

Presenter: MOTTA, Mariele (University of Geneva)



28th Texas Symp … / Report of Contributions The Effective Strength of Gravity a …


The Effective Strength of Gravity and the scale ofInflation


At any given energy, gravitational interactions have a strength set by a characteristic scale M∗,inferred from amplitudes calculated in an effective theory with a strong coupling scale M∗∗. Theseare in general different from each other andMpl, the macroscopic strength of gravity as determinedby (laboratory scale) Cavendish experiments. We explore several consequences of this fact forinflationary cosmology and CMB observables.

Primary author: PATIL, Subodh

Presenter: PATIL, Subodh



28th Texas Symp … / Report of Contributions Accretion and rotation power in m …


Accretion and rotation power in ms pulsarsWednesday, December 16, 2015 4:45 PM (25 minutes)

Neutron stars in low mass X-ray binaries can be spun-up to millisecond rotational periods byaccreting the matter transferred by a companion star. When the rate of mass transfer decreasesat the end of this Gyr-long X-ray bright phase, a radio pulsar powered by the rotation of theneutron star magnetic field turns on. Recently, the evolutionary link between these two classesof sources was finally proven by the XMM-Newton discovery of a millisecond pulsar observed toswing between accretion (X-ray bright) and rotation (radio bright) pulsar behaviour. This sourceis the prototype of a new class of transitional systems thatalternate between accretion and rotation-powered states in response to variations of the rate ofmass in-flow, on time scales as short as a couple of weeks. Observations of this and other similarsystems indicatethat transitions to the accretion phase not only involve bright X-ray outbursts, but also a fainterintermediate X-ray state, possibly caused by centrifugal inhibition of the matter in-fall. I willsummarize the main observed properties, as well as prospects of finding more sources of thisnewly established class.

Primary author: Dr PAPITTO, Alessandro (Space Science Institute Barcelona (ICE) CSIC-IEEC)

Presenter: Dr PAPITTO, Alessandro (Space Science Institute Barcelona (ICE) CSIC-IEEC)



28th Texas Symp … / Report of Contributions NuSTAR and XMM-Newton Obser …


NuSTAR and XMM-Newton Observation of SAXJ1808.4-3658 during the latest outburst


We will present spectral and timing analysis of NuSTAR and XMM-Newton data of the AccretingMillisecond Pulsar SAX J1808.4-3658 during its latest outburst in April 2015.We will discuss a high-quality broad band (2-80 keV) spectrum where the reflection component isclearly present, in line with previous results.Using DDT XMM-Newton data, we derived updated values for the spin and the orbital period ofthe source.We will discuss the secular evolution of these parameters in the frameworkof conservative versus non-conservative evolutionary scenarios.

Primary author: Prof. DI SALVO, Tiziana (University of Palermo)

Co-authors: Dr PAPITTO, Alessandro (Institut de Ciències de l’Espai (IEEC-CSIC)); Dr RIGGIO,Alessandro (University of Cagliari); Dr SANNA, Andrea (University of Cagliari); Mr GAMBINO, An-gelo (University of Palermo); Dr PINTORE, Fabio (University of Cagliari); Prof. BURDERI, Luciano(University of Cagliari); Mr MATRANGA, Marco (University of Palermo); Prof. IARIA, Rosario (Uni-versity of Palermo)

Presenter: Prof. DI SALVO, Tiziana (University of Palermo)



28th Texas Symp … / Report of Contributions Quasi-Static Solutions for Compac …


Quasi-Static Solutions for Compact Objects inChameleon Models


It has been suggested that a scalar field φ non-minimally coupled to matter could be responsiblefor the observed accelerated expansion of the Universe. However, the fact that we are able tomeasure its effect only on cosmological scales but not on local ones, such as that of our solar system,might be the consequence of a screening mechanism. This is the essence of the Chameleon model.Understanding its viability requires solving the field equations in the transition regime where thescalar field transitions from a region of high density to the outer region where it plays the role ofthe Dark Energy. In this work we analyze quasi-static spherically symmetric solutions for objectssuch as standard stars and more compact objects like white dwarfs and neutron stars, by solvingthe Tolman-Oppenheimer-Volkoff equations coupled with the Klein-Gordon equation in a quasistatic regime. We derive a solution that takes into account the background expansion withoutneeding to introduce an artificial cosmic matter corresponding to a non-spatially flat metric. Theinterior of the star is characterized using a constant density (incompressible) model and a morerealistic polytropic equation of state. The increase of compactness that we observe in case of agood screening (thin shell) allows to put serious constraints on the Chameleon mechanism and itsviability using astrophysical compact objects.

Primary author: Dr MUSCO, Ilia (Laboratoire Univers et Théories (LUTH) - Observatoire deParis)

Co-authors: MOTA, David F. (University of Oslo); GIL FERREIRA, Pedro; CORASANITI, PierStefano (CNRS & Observatoire de Paris)

Presenter: Dr MUSCO, Ilia (Laboratoire Univers et Théories (LUTH) - Observatoire de Paris)



28th Texas Symp … / Report of Contributions Status of the European Pulsar Tim …


Status of the European Pulsar Timing ArrayThursday, December 17, 2015 4:36 PM (21 minutes)

The European Pulsar Timing Array is a collaboration between European research institutes andradio observatories that was established in 2006. The EPTA makes use of the five largest radiotelescopes at decimetric wavelengths in Europe: the Effelsberg Radio Telescope, the Lovell RadioTelescope, the Nançay Radio Telescope, the Westerbork Synthesis Radio Telescope and the SardiniaRadio Telescope. The main goal of the EPTA is the direct detection of gravitational waves usinghigh-precision timing of an ensemble of millisecond pulsars. We will present here the status of theEPTA and show some of the latest pulsar timing results obtained with nearly 20 years of data.

Collaboration

European Pulsar Timing Array (EPTA)

Primary author: DESVIGNES, Gregory

Presenter: DESVIGNES, Gregory



28th Texas Symp … / Report of Contributions The POLARBEAR experiment pro …


The POLARBEAR experiment probing the cosmicmicrowave background polarization


The B-mode polarization of the cosmic microwave background (CMB) is a uniquewindow on fundamental questions in physics. The mass of the neutrinos and theproperties of the dark energy affect the structure formation, the gravitationallensing exerted by these structures on CMB results in a B-mode signal at smallscales. The large scales of the B-mode spectrum convey fundamental information onthe primordial universe, such as the energy scale and other properties ofinflation.

As the sensitivity of the instruments has approached the level of the B-modessignal, its measurements have become of major interest in cosmology. At theforefront in this quest, POLABEAR is a ground based telescope located in the Atacamadesert (Chile), at nearly 5200 m of altitude. With a 3.5 arcmin resolution and a1274 polarization sensitive bolometers, POLABEAR has beenobserving three 10 deg2 CMB patch at 150 GHz since 2012.

Using the data of the first observational campaign, which ended in may 2013POLABEAR provided indirect measurements of B-modes either via cross-correlation ofits maps with the Herschel cosmic infrared background maps (on 4 σ level), orfrom an analysis of 4-point moments of the polarization maps only (4.2 σ).A direct measurement of the B-mode power was also delivered finding an evidence(97.5 % c.l.) for non-zero sky power consistent with the predicted lensingB-mode signal. Furthermore, POLABEAR recently set new constraints onthe cosmic birefringence and primordial magnetic fields.

In this talk I will describe these results in detail as well as present the plansfor the future of the POLABEAR experiment. POLABEAR 2 and the Simons Array will increasethe sensitivity and have multiple frequency bands for a better rejection of the foreground signals.

Collaboration

POLARBEAR collaboration

Primary author: POLETTI, Davide

Presenter: POLETTI, Davide



28th Texas Symp … / Report of Contributions The nature of trapping horizons in …


The nature of trapping horizons in collapses formingblack holes


In the context of gravitational collapse to form a black hole, one sees the appearance of innerand outer trapping horizons (foliated by marginally trapped surfaces), as was already noted innumerical calculations in the 1960s. This phenomenology has acquired new interest in connectionwith discussions of the Hayward unified first law of black hole dynamics. We have investigatedthe nature of the inner and outer horizons (ie whether they are spacelike, timelike or null), makingcontact with the Misner-Sharp formalism used in calculations for collapse of spherically symmetricfluid configurations to form black holes. By means of numerical simulations, we have followed theR=2M condition dynamically during the gravitational collapse, and have found that the nature ofthese trapping horizons is given by a very simple expression depending on the equation of state,related also to the velocity of the horizon with respect the collapsing fluid. Whether these horizonsare spacelike or timelike plays an important role in in classical depletion and quantum evaporationof black holes because only timelike or null horizons allow particles to pass through. We haveobserved different behaviours for the cases of stellar collapse and primordial black hole formationwithin an expanding Universe, resulting from the different nature of the matter involved. In thistalk we will present results from our investigations.

Primary author: Dr MUSCO, Ilia (Laboratoire Univers et Théories (LUTH) - Observatoire deParis)

Co-authors: Dr HELOU, Alexis (APC, Observatoire de Paris); Prof. MILLER, John (Department ofPhysics (Astrophysics) University of Oxford (UK), S.I.S.S.A. Trieste (Italy))

Presenter: Dr MUSCO, Ilia (Laboratoire Univers et Théories (LUTH) - Observatoire de Paris)



28th Texas Symp … / Report of Contributions Gravitational Waves from a Dark S …


Gravitational Waves from a Dark SectorWednesday, December 16, 2015 2:42 PM (21 minutes)

A large class of models with a composite dark sector undergo a strong first order phase transitionin the early universe, which could lead to a detectable gravitational wave signal. I will summarisethe basic conditions for a strong first order phasetransition for SU(N) dark sectors, calculate the gravitational wave spectrumand show that, depending on the dark confinement scale, it can be detected at eLISA orin pulsar timing array experiments. The gravitational wave signal provides a unique testof the gravitational interactions of a dark sector, and we discuss the complementarity with con-ventional searches for new dark sectors.

Primary author: SCHWALLER, Pedro Klaus

Presenter: SCHWALLER, Pedro Klaus



28th Texas Symp … / Report of Contributions The Radio Evolution of the Galacti …


The Radio Evolution of the Galactic Center MagnetarThursday, December 17, 2015 5:15 PM (20 minutes)

While the radio emission of magnetars is notable for its peculiar spectrum and significant variabil-ity, the behavior of the Galactic Center magnetar is odd for even this class of neutron stars. In thistalk, I will present the broadband spectrum and high frequency (44 GHz) properties of this magne-tar in early to mid 2014, when the source transitioned from a fairly constant radio flux and pulseprofile to significant variability in both. These results provide important information regardingthe physical processes responsible for this transformation.

Primary author: D GELFAND, Joseph

Presenter: D GELFAND, Joseph



28th Texas Symp … / Report of Contributions Parity odd CMB power spectrum v …


Parity odd CMB power spectrum via helicalmagnetic field.


In this work we compute the temperature-polarization correlations(C_l^(TB) and C_l^(EB)) in the cosmic microwave background (CMB) generated by the presenceof causal primordial magnetic fields with a helical contribution.We analize the effect of an infrared cutoff in the power spectrum of causal fields on the cross-correlation and we compare our result with previous work.

Primary author: HORTUA, Hector Javier (Universidad Nacional)

Co-author: Dr CASTANEDA, Leonardo (Universidad Nacional)

Presenter: HORTUA, Hector Javier (Universidad Nacional)



28th Texas Symp … / Report of Contributions Primordial perturbations in a boun …


Primordial perturbations in a bouncing Universewith quintessence


In this work we investigate the features of the primordial power spectrum when it arises from acontracting phase in the context of a bouncing Universe.

We consider a toy model in which the Universe is dominated by a scalar field with an exponentialpotential, further on referred as the quintessence component. This choice is motivated by knownresults in the literature showing that such scalar field can behave like dust in the asymptotic pastand asymptotic future, implying the generation of an almost scale invariant spectrum for largescale modes, but can also exhibit a dark energy behavior in between.The dynamical system analysis of the background equations shows that the scalar field experi-ences an effective equation of state of dark energy type either in the contracting phase or in theexpanding phase of a quantum bouncing model, but not in both.

The first scenario is an exercise about how a quintessence field playing the role of dark energycould add new features in the power spectrum if it was present in a contracting phase. The secondis closer to realistic cosmological models where dark energy is present in the expanding phase,but is absent in the contracting phase. Both deserve attention, and are first approximations tothe development of realistic approaches to adress the problem of structure formation in bouncecosmologies with dark energy.

Primary authors: BACALHAU, Anna Paula (Centro Brasileiro de Pesquisas Físicas); Prof. PIN-TO-NETO, Nelson (Centro Brasileiro de Pesquisas Físicas)

Presenter: BACALHAU, Anna Paula (Centro Brasileiro de Pesquisas Físicas)



28th Texas Symp … / Report of Contributions Moving observed Short GRBs both …


Moving observed Short GRBs both off-axis and intothe local Universe


Short Gamma Ray Bursts (SGRBs) are among the best source candidates of simultaneous electro-magnetic radiation and gravitational waves (GWs) in the frequency range covered by the imminentsecond generation laser interferometer detectors Advanced LIGO and Advanced Virgo.SGRB afterglow properties in the electromagnetic spectrum (e.g. photon flux intensity, variabilitytime scale) can be very different one with the other, and the statistics available so far may provideaverage properties not representative of the population.In this work we compute the expected afterglow emission of a sample of short GRBs as they werewithin the GW detector horizons, and if they were detected from line of sights out of the jet cone(i.e. off-axis), that for geometrical reasons is a more likely configuration.We discuss our results in the context of the observational strategies to simultanously detect thesesources both in GW and electromagnetic radiations with present and future facilities.

Primary author: STRATTA, Giulia (Urbino University)

Co-authors: Dr DE CESARE, Giovanni (IASF-Bologna); Dr GRECO, Giuseppe (Urbino Univer-sity); Dr BRANCHESI, Marica (Urbino University)

Presenters: Dr DE CESARE, Giovanni (IASF-Bologna); STRATTA, Giulia (Urbino University); DrGRECO, Giuseppe (Urbino University); Dr BRANCHESI, Marica (Urbino University)



28th Texas Symp … / Report of Contributions Cosmic ray positrons and antiprot …


Cosmic ray positrons and antiprotons: implicationsfor Dark Matter


Using the updated proton and helium fluxes just released by the AMS-02 experiment we reevaluatethe secondary astrophysical positron and antiproton fluxes. We compare our results with thepositron flux and the preliminary antiproton to proton ratio, both measured by AMS-02. The mainuncertainties for the theoretical calculation are assessed. For positrons, we test the possibility toexplain the measured excess with a Dark Matter scenario and we probe the parameter space for theDark Matter component. Then, we examine the possibility to explain the data with the contributionof one single pulsar. For antiprotons, we find no unambiguous evidence for a significant excesswith respect to expectations. Yet, some preference for a flatter energy dependence of the diffusioncoefficient starts to emerge. Also, we provide a first assessment of the room left for a Dark Mattercomponent, deriving new stringent constraints.

Primary author: BOUDAUD, Mathieu (LAPTh Annecy France)

Presenter: BOUDAUD, Mathieu (LAPTh Annecy France)



28th Texas Symp … / Report of Contributions Broadband characterisation and p …


Broadband characterisation and physicalimplications from the most extreme X-ray flaring

activity of the high-peaked BL Lac Mrk 501Tuesday, December 15, 2015 2:21 PM (21 minutes)

The high-frequency-peaked BL Lac object Markarian 501 is a very high energy (VHE, E>100 GeV)emitter located in our extragalactic neighborhood (z=0.034). The source can be detected in the VHEband during low state, what makes this target an ideal source for long-term multi-wavelengthstudies covering the entire electromagnetic spectrum. During a multi-wavelength campaign in2014, the source showed the highest X-ray activity observed by Swift-XRT during the last decade.The source displayed very hard spectra at X-rays and gamma-ray energies with variability on daytimescales. The distortion of the broadband SED strongly suggests the existence of, at the very least,an extra component with ultra-energetic and relatively narrow electron energy distribution, whichhad never been seen before for Mrk501. In the conference I will report about this unprecedentedflaring event and its physical implications.

Collaboration

on behalf of the MAGIC and Fermi-LAT collaboration

Primary author: BECERRA GONZALEZ, Josefa (NASA GSFC)

Co-authors: PANEQUE CAMARERO, David (Instituto de Fisica de Altas Energias (IFAE)); TAVEC-CHIO, Fabrizio (INAF); ISHIO, Kazuma (MPI); NODA, Koji (Max-Planck-Institute for Physics); PERRI,Matteo (ASI Science Data Center)

Presenter: BECERRA GONZALEZ, Josefa (NASA GSFC)



28th Texas Symp … / Report of Contributions Evidence for quasi-periodic modul …


Evidence for quasi-periodic modulation in thegamma-ray blazar PG 1553+113


For the first time a gamma-ray and multiwavelength nearly-periodic oscillation in an active galac-tic nucleus is reported using the Fermi Large Area Telescope (LAT). A quasi-periodicity in thegamma-ray flux (E>100 MeV and E>1 GeV) is observed from the well-known GeV/TeV BL Lac ob-ject PG 1553+113 (Ackermann et al. submitted). The significance of the 2.18 +/- 0.08 year-periodgamma-ray modulation, seen in 3.5 oscillation maxima observed, is supported by significant cross-correlated variations observed in radio and optical flux light curves, through data collected in theOVRO, Tuorla, KAIT, and CSS monitoring programs and Swift UVOT. The optical cycle, appearingin about 10 years of data, has a similar period, while the radio-band oscillation observed at 15 GHzis less regular and coherent. The available X-ray flux data obtained by Swift XRT appears also to belinearly correlated with the gamma-ray flux. Further long-term multi-wavelength monitoring ofthis blazar may discriminate among the possible explanations for this first evidence of periodicity.In this view a multi-wavelength campaign, from radio to VHE gamma rays was started in 2015(Hughes et al. this conference).

Collaboration

Fermi LAT Collaboration

Primary authors: STAMERRA, Antonio (INAF-OATo / SNS-Pisa); THOMPSON, David (NASAGoddard Space Flight Center); CUTINI, Sara (ASI Science Data Center - INFN); LARSSON, Stefan (TheOskar Klein Centre, KTH); Dr CIPRINI, Stefano (ASI Science Data Center - INFN)

Presenter: STAMERRA, Antonio (INAF-OATo / SNS-Pisa)



28th Texas Symp … / Report of Contributions A Uniformly Selected, All-Sky Opt …


A Uniformly Selected, All-Sky Optical AGN Catalogfor UHECR Correlation


Studies discerning whether there is a significant correlation between ultra high energy cosmic ray(UHECR) arrival directions and optical AGN are hampered by the lack of a uniformly selected andcomplete all-sky optical AGN catalog. To remedy this, we are preparing such a catalog based onthe 2MASS Redshift Survey (2MRS), a spectroscopic sample of ∼ 44, 500 galaxies complete to a Kmagnitude of 11.75 over 91% of the sky. We have analyzed the available optical spectra of these2MRS galaxies (∼ 80% of the galaxies), in order to identify the AGN amongst them with uniformcriteria. Although the selection is uniform, the spectra were taken with different instruments (themajority from four different observatories). We present not only the catalog but an assessmentof its homogeneity and completeness. Correlations between this well-characterized catalog andUHECRs published by the Pierre Auger Observatory and its implications will also be discussed.

Primary author: ZAW, Ingyin (NYU Abu Dhabi)

Co-author: FARRAR, Glennys (NYU)

Presenter: ZAW, Ingyin (NYU Abu Dhabi)



28th Texas Symp … / Report of Contributions The LZ Dark Matter detector


The LZ Dark Matter detectorWednesday, December 16, 2015 6:30 PM (3 minutes)

LZ is a second-generation dark-matter experiment designed to achieve unprecedented sensitivityto weakly interacting massive particles (WIMPs) of masses from a few GeV/c to hundreds of TeV/c2.With total liquid xenon mass of about 10 tonnes, LZ is planned to achieve a sensitivity to WIMP-nucleon spin-independent cross section approaching ∼2⋅10−48 cm2 in 3 years of operation. Thisrepresents an improvement of almost three orders of magnitude over current results, covering asubstantial range of theoretically-motivated dark matter candidates. We will present aspects ofLZ’s designs that permit achievement of this planned sensitivity.

Collaboration

LZ (LUX-Zeplin)

Primary author: GOMBER, Bhawna (University of Wisconsin (US))

Presenter: GOMBER, Bhawna (University of Wisconsin (US))



28th Texas Symp … / Report of Contributions Disentangling AGN and Star Form …


Disentangling AGN and Star FormationContributions in the Central Parsec of NGC 4945


NGC 4945, one of the closest starburst-AGN presents a unique laboratory for testing the interplaybetween AGN accretion and star formation. It is the brightest extragalactic source of hard X-raysbut is highly obscured below 10 keV. Its proximity allows for mapping the inner-most parsec of thegalactic nucleus using very long baseline interferometry of the unobscured 22 GHz water maseremission. Combining the sub-parsec scale maser map with X-ray and infrared images of largerscale structures allows for the disentangling of contributions from the AGN and star formation. Inthis system, the masers are found in the thick, clumpy, circumnuclear disk as well as the shocks thattrace the base of the X-ray and infrared wind. The masers pinpoint the location of the supermassiveblack hole and provide evidence that the wind is driven by the AGN rather than the star formation.Furthermore, some of the maser emission in the disk does not follow Keplerian rotation, indicatingfragmentation and star formation in the sub-parsec scale disk.

Primary author: ZAW, Ingyin (NYU Abu Dhabi)

Co-author: Prof. GREENHILL, Lincoln (Harvard-Smithsonian Center for Astrophysics)

Presenter: ZAW, Ingyin (NYU Abu Dhabi)



28th Texas Symp … / Report of Contributions Flat spectrum radio quasars at very …


Flat spectrum radio quasars at very high energies:the new detection of PKS 1441+25


The detection of Flat Spectrum Radio Quasars (FSRQs) in the Very High Energy (VHE, E>100GeV) range is challenging, mainly due to their steep soft spectra in this energy band. Thus far,only five FSRQs are known to be VHE gamma-ray emitters, all of which have been detected by theMAGIC telescopes, which made the first VHE detection of four of them. Observations in the VHEband are crucial to understand their emission, especially to constrain the location of the emittingregion within the jet due to the absorption from their broad line region (BLR). The most recentmember of the VHE FSRQ family is PKS 1441+25 (z=0.940) which was detected in this band forthe first time by the MAGIC telescopes on April 2015. The observations were triggered by theflaring activity detected by the Fermi-LAT at High Energies (HE, 100 MeV < E < 100 GeV). Asidefrom the gravitationally lensed VHE blazar QSO B0218+357 (z = 0.944), also detected by MAGIC,PKS 1441+25 is the most distant VHE blazar observed to date. For the first time, the VHE gamma-ray spectrum was used to indirectly probe the extragalactic background light at redshifts out to z ~0.94 from sensitive ground Cherenkov observations in the energy range from 40 to 250 GeV. In thiscontribution we will review the last results on the observations of VHE FSRQs with the MAGICtelescopes in a multi-wavelength context with special focus on the new detection of PKS 1441+25.

Collaboration

on behalf of the MAGIC and Fermi-LAT collaboration

Primary author: BECERRA GONZALEZ, Josefa (NASA GSFC)

Co-authors: MORALEJO, Abelardo (IFAE); LINFORS, Elina (Tuorla Observatory); TAVECCHIO,Fabrizio (INAF); MANGANARO, Marina; NIEVAS, Miguel (UCM)

Presenter: BECERRA GONZALEZ, Josefa (NASA GSFC)

28th Texas Symp … / Report of Contributions Recent Science Highlights from V …


Recent Science Highlights from VERITASWednesday, December 16, 2015 2:50 PM (25 minutes)

VERITAS is a very-high-energy (VHE, Ex2273100 GeV) gamma-ray observatory that has beenin full scientific operation since 2007. A series of upgrades has provided significant sensitivityincreases and improved low-energy performance, greatly enhancing the scientific capabilities ofVERITAS. The VERITAS science program includes a full complement of observations of Galac-tic (pulsars, pulsar-wind nebulae, supernova remnants, binary systems) and extragalactic objects(blazars, radio and starburst galaxies, gamma-ray bursts), in addition to cosmic ray studies andindirect searches for dark matter. To date, VERITAS has detected more than 50 sources of VHEgamma rays from eight source classes. Highlights of the most recent VERITAS results will bepresented.

Collaboration

The VERITAS Collaboration

Primary author: QUINN, John (University College Dublin)

Presenter: QUINN, John (University College Dublin)



28th Texas Symp … / Report of Contributions The SST-1M Project of the Cheren …


The SST-1M Project of the Cherenkov TelescopeArray: Status and Physics Perspectives


The SST-1M telescope is one of the prototypes under construction proposed to be part of the futureCherenkov Telescope Array.It uses a standard Davis-Cotton design for the optics and telescope structure, with a dish diameterof 4 meters and a large field-of-view of 9 degrees.An innovative camera with Silicon Photomultipliers and fully digital readout and trigger electron-ics, DigiCam, has been designed and its first prototype will be installed on the existing telescopestructure in 2016.

In this contribution we give a general overview of the project status.The key existing performance results and commissioning data will be briefly presented while theemphasis will be put on the science case of the SST telescopes in the framework of the CherenkovTelescope Array.Main target of these small telescopes is to investigate the very high energy sky above few TeVwith unprecedented sensitivity, making them the ideal probe of hadronic mechanisms in galacticsources and Pevatrons.Moreover, the large field of view will allow to perform wide surveys and improve dark mattersearches.

Collaboration

SST-1M consortium and CTA consortium

Primary author: HELLER, Matthieu (Universite de Geneve (CH))

Co-author: PRANDINI, Elisa (Universite de Geneve (CH))

Presenter: HELLER, Matthieu (Universite de Geneve (CH))



28th Texas Symp … / Report of Contributions Kinetic simulations of relativistic h …


Kinetic simulations of relativistic harmonicmagnetic equilibria


We will present the results of kinetic particle-in-cell numerical simulations of relativistic harmonicmagnetic equilibria, so called “ABC fields”. These equilibria have been recently shown by relativis-tic magnetofluid simulations to be generally unstable. An ideal plasma instability leads to theformation of dynamical current layers where magnetic energy is dissipated via reconnection andparticles are accelerated efficiently. This concept may provide a viable generic scenario for the pro-duction of rapid gamma-ray and X-ray flares in strongly magnetized astrophysical environments,such as relativistic jets of active galaxies, gamma-ray bursts, pulsar wind nebulae (Crab), or theGalactic Center source Sgr A*.

Primary author: Dr NALEWAJKO, Krzysztof (Stanford University)

Co-authors: Dr ZRAKE, Jonathan (Stanford University); Prof. BLANDFORD, Roger (Stanford Uni-versity); Dr EAST, William (Stanford University); Mrs YUAN, Yajie (Stanford University)

Presenter: Dr NALEWAJKO, Krzysztof (Stanford University)



28th Texas Symp … / Report of Contributions Particle acceleration in Eta Carina …


Particle acceleration in Eta Carinae: the expectedand unexpected


The Fermi Large Area Telescope (LAT) observed for the first time ever two consecutive ηCarinaeperiastron passages. The large field of view of the instrument, its performing sensitivity and ho-mogeneous exposition offers a continuous observation above 100 MeV of the ηCarinae region onthe last 7 years. ηCarinae is a binary system hosted in the Carina nebula. Its luminous blue vari-able and O stars emit dense and high-velocity gaseous winds that make this system a promisingparticle acceleration site from which very high energy γ-ray emission can be expected. No otherinstruments before Fermi-LAT have ever detected the high energy emission coming from ηCarinaein 2 consecutive periastron passages. A maximum likelihood analysis on the recent 7-year data ofthe Carina region clearly detects an high energy emission above 10 GeV during both periastronpassages (> 5σ) from a 95% c.l. location strongly in agreement with the nominal position ofηCarinae. A spectral analysis gives faint hints of an hardening of the spectral index immediatelybefore both periastron passages. Contrarily to the expectation that the closeness of the two starscould increase the efficiency of the outflow enhancement into particle acceleration, a temporalanalysis indicates that the flux does not show a strong periodicity.ηCarinae system with its spectral variation and lightcurve represents a very good candidate to testand constraints future acceleration models for colliding wind binaries.

Collaboration

ISDC, Université de Genève, Observatoire de Genève

Primary author: BALBO, Matteo (Université de Genève)


Presenter: BALBO, Matteo (Université de Genève)



28th Texas Symp … / Report of Contributions First-order Fermi acceleration at p …


First-order Fermi acceleration at pulsar windtermination shock.


The Pulsar Wind Nebulae (PWNe) PSR B1259-63 has beenobserved to emit periodic GeV flares, whose power can becomparable to the total pulsar spin-down luminosity.Because of the short timescale involved,these photons are likely to beproduced via inverse Compton scattering of stellar photons orSynchrotron radiation by a population of very energetic electrons(from GeV to TeV energies) in proximity of the wind termination shock (TS).This perpendicular shock is created bythe interaction between the magnetised,relativistic, electron-positron wind launched by thepulsar with the companion star outflow.When the rotational frequency of the pulsar is greater than the localplasma frequency in the wind, a shock precursor forms ahead of the TS,where the Poynting flux is dissipated. This condition is satisfiedat the TS in a gamma-ray binary when the system is far fromperiastron, but not necessarily when the stars are inclose proximity to each other (Mochol & Kirk 2013).It is stll unclear whether and how this structure canaccelerate electrons to high energies.We investigate this in a two-step procedure.Firstly, a 1-dimensional, relativistic,2-fluid code is used to reproduce the turbulent fieldsin the equatorial plane at the location of the TS.We numerically integrate test particle trajectories inthe background fields of a steady configurationof the precursor realised for an upstream Lorentz factorΓ = 40 and a magnetisation parameter σ = 10.We follow each particle until iteither escapes downstream after transmission or upstreamafter reflection. We find that ∼ 50% of the incoming particlesare reflected upstream by the turbulent fields for these parameters. Secondly, we simulate Fermi-likeacceleration by supplementing magnetic fluctuations withprescribed statistical properties both in the pulsar wind upstream of the shock,and in the nebula downstream of the shock,where the field is assumed to have been dissipated.The resulting stochastic trajectories are numerically integrated (Achterberg & Kruells 1992).We compare the power-law index and the angular distributionof accelerated particles with the same quantities obtainedwith a numerical simulation where the average magnetic field is null


28th Texas Symp … / Report of Contributions First-order Fermi acceleration at p …

on both sides of the shock and the only source of deflectionfor energetic particles is the scattering off magnetic irregularities(Achterberg et al. 2001).We argue that the proposed scenario is relevant for PWNe in γ-raybinaries such as PSR B1259-63.

Primary author: Mr GIACCHE‘, Simone (Max-Planck Institute for Nuclear Physics)

Co-authors: Prof. KIRK, John (Max-Planck Institute for Nucear Physics); Dr AMANO, Takanobu(Department of Earth and Planetary Science, University of Tokyo)

Presenter: Mr GIACCHE‘, Simone (Max-Planck Institute for Nuclear Physics)



28th Texas Symp … / Report of Contributions Rapid variations of polarisation in …


Rapid variations of polarisation in X-ray binariesWednesday, December 16, 2015 5:38 PM (21 minutes)

Recently, evidence for synchrotron emission in both black hole and neutron star X-raybinaries has been mounting, from optical/infrared spectral, polarimetric, and (possibly)fast timing signatures. Time-resolved optical and infrared polarimetric observations of X-ray bi-naries are presented. It is found that the infrared emission of GX 339-4 in the hardstate contains variable polarization on timescales of < 60 seconds. In the first study ofits kind, we present strictly simultaneous time-series X-ray, UV, optical, infraredpolarimetry and radio observations of Cygnus X-2. Variability in the flux is tested forcross-correlations with all other wavelengths, and polarisation strength and angle iscross-correlated with flux variability. Correlated variability could be caused by a disc-jetcoupling mechanism on short timescales. The results are compared to other neutronstar XRBs such as Sco X-1, which also has a variable polarisation signature atoptical/infrared wavelengths. The synchrotron emission of jets can be highly linearlypolarised, depending on the configuration of the magnetic field, and the magnetic fieldsnear the jet base in these systems appear to be turbulent, variable and aligned with thejet axis. This probes the physical conditions in the accretion (out)flow and demonstratesa new way of connecting inflow and outflow, using both rapid timing and polarisation.The implications for future measurements of X-ray polarisation are discussed. We alsopresent a detection of polarisation in the quiescent black hole system Swift J1357.2-0933 which originates from its highly variable infrared emission. These results likelyconstrain the magnetic structure in the inner regions of the jets launched from accretingX-ray binaries.

Collaboration

New York University Abu Dhabi

Primary author: RUSSELL, Dave

Presenter: RUSSELL, Dave

28th Texas Symp … / Report of Contributions Gaps in black holes magnetospheres


Gaps in black holes magnetospheresWednesday, December 16, 2015 5:15 PM (3 minutes)

We consider the possible existence and observational consequences of the so-called vacuum “gaps”in the SMBH force-free magnetospheres in RIAF type sources. The gaps are the sites with a lackof the volume charge density in comparison to the plasma-filled force-free regions of the mag-netosphere. They are analogous to the gaps in the pulsars magnetospheres. In such gaps directacceleration of charged particles by unscreened electric field could occur. It is vacuum gaps thatcould play an important role in the process of the plasma filling of the BH magnetosphere and be-cause of the direct particle acceleration are also interesting from the point of view of the UHECRorigin problem.We analyse the gap properties by numerical modelling of the particle acceleration and radiationin the black hole magnetosphere, embedded into the accretion flows’ background radiation field.We show that for the some range of the RIAF parameters there are sharp features in the radiationspectrum at GeV-TeV energies, produced by the particles, accelerated in the gaps. The observationof these features would allow to verify the discussed model.

Primary author: PTITSYNA, Ksenia (INR Moscow, MSU Moscow, ISDC Geneve)

Co-author: NERONOV, Andrii (University of Geneva)

Presenter: PTITSYNA, Ksenia (INR Moscow, MSU Moscow, ISDC Geneve)



28th Texas Symp … / Report of Contributions Dualities and Symmetries of Galile …


Dualities and Symmetries of GalileonsWednesday, December 16, 2015 5:15 PM (20 minutes)

Galileons appear in the low-energy limit of several cosmologically motivated theories, e.g. MassiveGravity, Bigravity and DGP. Yet we are only just beginning to understand some of their features.I will discuss newly discovered dualities and enhanced symmetries for (subsets of) Galileons andhow they are related to scalar-theories of gravity and Massive gravity/Bigravity in particular.

Primary author: NOLLER, Johannes (University of Oxford)

Presenter: NOLLER, Johannes (University of Oxford)



28th Texas Symp … / Report of Contributions The Quijote experiment: project o …


The Quijote experiment: project overview and firstresultsMonday, December 14, 2015 2:25 PM (20 minutes)

The QUIJOTE (Q-U-I JOint TEnerife) experiment is a new polarimeter working in the frequencyrange 10-40 GHz, and designed to characterize the primordial B-mode anisotropy of the CMBpolarization down to a sensitivity in the tensor-to-scalar ratio of r~0.05, and to measure the levelof the polarization of low-frequency Galactic foregrounds (the synchrotron and the anomalousdust emissions). The project consists of two telescopes and three instruments which will surveya large sky area (20000 sq-deg) from the Teide Observatory (Tenerife) to provide Q and U mapsof high sensitivy (1-3 µK/beam in a deeper region of 3000 sq-deg). The first telescope and theMulti-Frequency Instrument (MFI) are operative since November 2012 in the frequency range 10-20 GHz. The second telescope and two additional instruments, respectively at 30 and 40 GHz, arecurrently under construction. These two experiments will provide Q and U maps with a sensitivitybetter than 1 µK/beam. In this talk I will discuss the status of this project, its future goals, andwill present the first results obtained with the MFI, with emphasis on the inferred limits on thepolarization fraction of the anomalous dust emission, and on the characterization of the propertiesof the synchrotron polarization in various regions that we have observed.

Primary author: Dr GÉNOVA SANTOS, Ricardo (Instituto de Astrofísica de Canarias)

Presenter: Dr GÉNOVA SANTOS, Ricardo (Instituto de Astrofísica de Canarias)



28th Texas Symp … / Report of Contributions Accurate Phenomenological Wave …


Accurate Phenomenological Waveform Models forBlack Hole Coalescence in the Frequency Domain


This talk will discuss the current state of the phenomenological waveform approach for non-precessing black hole binaries, and recent numerical relativity simulations used in the modellingand performed with the BAM code. Using these simulations, we have extended the calibrationrange of our inspiral-merger-ringdown model to mass ratio 18. The talk will in particular alsodiscuss the anatomy of the merger-ringdown waveform in the frequency domain, and the con-struction of hybrid post-Newtonian-numerical relativity waveforms.

Primary author: HUSA, Sascha

Co-authors: Dr BOHÉ, Alejandro (Albert Einstein Institute Potsdam); HANNAM, Mark (Universityof Cardif); Dr PÜRRER, Michael (Albert Einstein Institute Potsdam); Mr KHAN, Sebastian (CardiffUniversity); Mr JIMENEZ-FORTEZA, Xisco (Universitat de les Illes Balears)

Presenter: HUSA, Sascha



28th Texas Symp … / Report of Contributions Angular momentum loss by gravit …


Angular momentum loss by gravitational radiationin binaries with black hole


In this study, we present angular momentum loss mechanism through gravitational radiation forthe selected X-ray binary systems. Gravitational radiation time-scale is estimated for each selectedsystem. In addition, their gravitational wave amplitudes are also estimated and their detectabilitywith gravitational wave detectors has been discussed.

Collaboration

Kocak, D., Yakut, K.

Primary author: Ms KOCAK, Dolunay (University of Ege)

Co-author: YAKUT, Kadri (University of EGE)

Presenters: Ms KOCAK, Dolunay (University of Ege); YAKUT, Kadri (University of EGE)



28th Texas Symp … / Report of Contributions Catalog of isolated emission episo …


Catalog of isolated emission episodes in Gamma-raybursts from Fermi, Swift and BATSE

The complexity of temporal profiles of the prompt emission in Gamma-Ray Bursts (GRBs) is stillnot well understood. Several GRBs show distinct emission episodes, separated with a quiescentinterval during which the gamma-ray flux falls to the background level. We present a large catalogof long GRBs with isolated emission episodes from a systematic search in Fermi, Swift and BATSE.The properties of the events prior and after the main emission (the event with the higher peakflux) are statistically similar, possibly indicating a common origin. In several GRBs, the emissionextends far beyond T90, which may have significant consequences for the identification of non-electromagnetic counterparts.

Primary author: CHARISI, Maria (Columbia University)

Presenter: CHARISI, Maria (Columbia University)


28th Texas Symp … / Report of Contributions Relativistic effects with cross- …


Relativistic effects with cross-correlationsMonday, December 14, 2015 2:42 PM (21 minutes)

I will discuss the galaxy clustering in a relativistic framework in terms of observable quantities,i.e angles and redshifts. A relativistic description includes terms beyond the Kaiser approximation(doppler effects and galaxy evolution), gravitational potentials and integrated terms (cosmic mag-nification, integrated Sachs-Wolfe and Shapiro time-delay). These terms are currently neglected,but they might play a role in future surveys which probe larger scales. I will show that by corre-lating different probes, or by using the so-called multi-tracer technique, some relativistic effectscould give a non-negligible contribution to the galaxy clustering observables.

Primary author: DI DIO, Enea (OATs-INAF)

Presenter: DI DIO, Enea (OATs-INAF)



28th Texas Symp … / Report of Contributions Angular momentum loss by gravit …


Angular momentum loss by gravitational radiationin x-ray binaries with neutron stars


In this study, we present angular momentum loss mechanism through gravitational radiation forthe selected system with neutron stars and gravitational radiation time-scale is estimated for them.

Collaboration

İcli,T., Yakut, K.

Primary author: İÇLİ, Tuğçe


Presenters: YAKUT, Kadri (University of EGE); İÇLİ, Tuğçe



28th Texas Symp … / Report of Contributions GRS 1915+105 and its spectral vari …


GRS 1915+105 and its spectral variability from thekeV to the MeV band


The microquasar GRS 1915+105 features well known spectral states that were never extensivelystudied up to the MeV range, where key spectral diagnostics are expected. We present hard X-rayobservations obtained in 15 Msec with Swift/BAT and INTEGRAL and spectra collected duringdifferent states up to 400 keV. These spectra can be successfully fitted by the EQPAIR model re-vealing continuous variations of the model parameters, including the inner radius of the accretiondisc, along the sequence of spectral states.

Primary author: Dr NIKOLAJUK, Marek (University of Bialystok)

Co-authors: XU, Ming (Chinese Academy of Sciences (CN)); WALTER, Roland (University ofGeneva)

Presenter: Dr NIKOLAJUK, Marek (University of Bialystok)



28th Texas Symp … / Report of Contributions Comments on the Effect of Frame …


Comments on the Effect of Frame DraggingWednesday, December 16, 2015 5:21 PM (3 minutes)

In this study, accurate and detailed solution of the frame-dragging process has been presentedwith a newly deduced equation of motion. Numerical solutions show that the results obtained inthis study are somewhat different than those results presented in Thirring (1918). Obtained resultshave been applied to various astrophysical mediums as case studies.

Collaboration

Ozbakir, I., Yakut, K.

Primary author: ÖZBAKIR, ismail


Presenters: YAKUT, Kadri (University of EGE); ÖZBAKIR, ismail



28th Texas Symp … / Report of Contributions Search for continuous gravitationa …


Search for continuous gravitational wave in EPTAdatasetThursday, December 17, 2015 4:57 PM (22 minutes)

We have searched for continuous gravitational wave (CGW) signals produced by individually re-solvable, circular supermassive black hole binaries (SMBHBs) in the latest EPTA dataset, whichconsists of ultra-precise timing data on 41 millisecond pulsars. Several algorithms have been usedand depending on the adopted detection algorithm, the 95% upper limit on the sky-averaged strainamplitude lies in the range 6 x 10^-15 < A < 1.5 x 10^-14 at 5 nHz < f < 7 nHz. The most robustupper limit – obtained via a full Bayesian analysis searching simultaneously over the signal andpulsar noise on the subset of our six best pulsars – is A ~10^-14. These limits, the most stringentto date at f < 10 nHz, exclude the presence of sub-centiparsec binaries with chirp mass Mc > 10^9solar masses out to a distance of about 25 Mpc, and with Mc > 10^10 solar masses out to a distanceof about 1 Gpc (z~ 0.2).

Collaboration

European Pulsar Timing Array

Primary author: Dr LASSUS, Antoine (Max Planck Institute für Radioastronomie)

Co-authors: PETITEAU, Antoine (Universite Paris-Diderot - CNRS); BABAK, Stanislav

Presenter: Dr LASSUS, Antoine (Max Planck Institute für Radioastronomie)

28th Texas Symp … / Report of Contributions The underlying simplicity of prece …


The underlying simplicity of precessing black-holebinariesWednesday, December 16, 2015 5:15 PM (20 minutes)

Modelling the inspiral, merger and ringdown of generic (i.e., precessing) black-hole binaries haslong been a major challenge for theoretical gravitational-wave astronomy. I will present a simplepicture of the underlying phenomenology of these systems, which has lead to a novel techniqueto produce accurate generic waveform models.

Primary author: HANNAM, Mark (Cardiff University)

Co-author: HUSA, Sascha

Presenter: HANNAM, Mark (Cardiff University)



28th Texas Symp … / Report of Contributions Relativistic chiral magnetohydrod …


Relativistic chiral magnetohydrodynamics andevolution of cosmological magnetic fields


If chiral (left-right) asymmetry is present in the plasma,the electric current, parallel to the magnetic field, appears. This is known as“chiral magnetic effect“. We demonstrate that this effect changes the dynamics of the magnetizedrelativistic plasma and present the proper equations of chiral relativistic magnetohydrodynamics,containing a new, axion-like, degree of freedom. There results are relevant for generation andevolution of cosmological magnetic fields in the electroweak epoch and are applicable to otherrelativistic plasmas.

Primary authors: Dr BOYARSKY, Alexey (Leiden University (NL)); RUCHAYSKIY, Oleg (EcolePolytechnique Federale de Lausanne (CH))

Presenters: Dr BOYARSKY, Alexey (Leiden University (NL)); RUCHAYSKIY, Oleg (Ecole Polytech-nique Federale de Lausanne (CH))



28th Texas Symp … / Report of Contributions 3FGL J1544.6-1125: radio imaging …


3FGL J1544.6-1125: radio imaging analysis of newesttransitional millisecond pulsar


Recently, Bogdanov & Halpern (2015) identified the unassociated Fermi gamma-ray source 3FGL~J1544.6−1125 as only the 4th known “transitional millisecond pulsar” (tMSP), a claim further bolstered byfollow-up observations by Bogdanov (2015). The tMSPs are a newly discovered class of binarysystems that transition between states as a radio millisecond pulsar and a low-mass X-ray binary(LMXB). In the LMXB state tMSPs show X-ray variability over ~10 − 100s, switching between‘high’ and ‘low’ luminosity modes, as well as infrequent ‘flares’. In the high mode, coherent X-raypulsations are seen, indicating channeled accretion onto the neutron star surface despite the verylow accretion rate, and offering the potential to study very low-level accretion onto neutron stars.A coordinated radio/X-ray campaign undertaken for PSR J1023 + 0038 showed that this tMSP ismuch brighter in radio than expected, and with rapidly variable and flat spectrum continuum emis-sion most likely associated with compact, self-absorbed jet (Deller et al. 2015). This strongly hintsat radiatively inefficient accretion flow where majority of accretion energy goes into an outflow.3FGL J1544.6−1125 is currently the only other system in the right state for detailed observationsto confirm whether efficient jet formation is common to all tMSPs, and would add a 4th importantdata point to the newly hypothesized radio/X-ray luminosity relationship for tMSPs. We havetherefore observed it with VLA four times over the period of several weeks. Preliminary resultsindeed show a behaviour similar to J1023, further strengthening the case for 3FGL J1544 beinga tMSP. I would be presenting results from this first ever observational campaign to detect thesource in radio.

Primary author: JAODAND, amruta (ASTRON- Netherlands Institute for Radio Astronomy)

Co-authors: DELLER, Adam; PATRUNO, Alessandro (L); Ms ARCHIBALD, Anne (Netherlands Insti-tute for Radio Astronomy); Mr BASSA, Cees (Manchester, University of (Jodrell Bank)); Mr MILLER-JONES,James (Curtin University of Technology); Mr HESSELS, Jason (Netherlands Institute for Radio Astron-omy); Mr MOLDON, Javier (Netherlands Institute for Radio Astronomy); WIJNANDS, Rudy (Universityof Amsterdam); Mr BOGDANOV, Slavko (Columbia University)

Presenter: JAODAND, amruta (ASTRON- Netherlands Institute for Radio Astronomy)



28th Texas Symp … / Report of Contributions CMB lensing - galaxy cross- …


CMB lensing - galaxy cross-correlationsThursday, December 17, 2015 3:24 PM (21 minutes)

Large scale structure in the universe causes gravitational lensing ofthe cosmic microwave background (CMB), which has now beenwell-measured by several CMB experiments. By cross-correlating CMBlensing with tracers of large scale structure (like galaxies), it ispossible to obtain new constraints on cosmology and a betterunderstanding of possible systematic errors in cosmological probes.

I will discuss the theoretical formulation, methods used in estimatingerrors, systematic checks to verify robustness, and cosmologicalimplications of cross-correlations between CMB lensing and galaxysurveys, and will present recent results of cross-correlation analyses.

Collaboration

SPT & DES collaborations

Primary author: Mr OMORI, Yuuki (McGill University)

Presenter: Mr OMORI, Yuuki (McGill University)



28th Texas Symp … / Report of Contributions Limits on the amplitude of the nan …


Limits on the amplitude of the nanohertzgravitational wave Universe from the European

Pulsar Timing ArrayThursday, December 17, 2015 5:19 PM (22 minutes)

The European Pulsar Timing Array (EPTA) was established in 2006 as a collaboration betweenEuropean research institutes and radio observatories. The key mission of the EPTA is the directdetection of nanohertz gravitational waves (GWs) using the high-precision timing of an ensembleof millisecond pulsars. The primary source of GWs in the nanohertz band is expected to be mergingsupermassive black hole binaries (SMBHBs). We will present recent results from the EPTA thatset limits on the amplitude of an isotropic, or anisotropic gravitational wave background, formedfrom the super position of signals from a large population of these SMBHBs, as well as limits on theamplitude of GWs from individual sources. Finally we will discuss recently introduced methods ofimproving the sensitivity of timing arrays to GWs by performing the analysis using profile data.

Collaboration

European Pulsar Timing Array

Primary author: Dr LENTATI, Lindley (Cambridge University)

Presenter: Dr LENTATI, Lindley (Cambridge University)



28th Texas Symp … / Report of Contributions Simulating the start of inflation fr …


Simulating the start of inflation frominhomogeneous initial conditions


A period of exponential expansion early in our cosmic history is usuallyinvoked to explain the large scale homogeneity and isotropy of the Universe.However, there remain important questions about the conditions under whichinflation can actually start when homogeneity is not assumed to begin with it.In this talk, I will present results from fully general-relativistic simulations used to understand thecircumstances underwhich a period of exponential expansion can eventually arise from initialconditions where the gradient and kinetic energy of the putative inflaton dominates overthe potential energy. This allows us to study what happens in a number of different cases, bothwhen using different inflaton potentials, as well as when considering a range of different scalesfor the inhomogeneities. In particular, we study the regime where the length scale of the inho-mogeneities is comparable to the average Hubble radius, and where the gravitational pull of theover-densities is strong enough to form black holes.

Primary author: Dr EAST, William (Stanford University)

Co-authors: LINDE, Andrei (Stanford University); SENATORE, Leonardo (Stanford University); KLE-BAN, Matthew (New York University)

Presenter: Dr EAST, William (Stanford University)



28th Texas Symp … / Report of Contributions MHD Turbulence and Particles


MHD Turbulence and ParticlesWednesday, December 16, 2015 3:24 PM (21 minutes)

MHD Turbulence is a strongly nonlinear dynamics of conductive fluids, e.g. plasma. Recentprogress in theory regarding almost all basic regimes of this dynamics – from how the magneticfield is generated (dynamo problem), to how turbulence is decaying, to what are the asymptoticscaling laws, allowed us to proceed with more observationally motivated questions. One of themis why almost all strongly magnetized environments are indeed observable, e.g. why such envi-ronments are infused with high-energy particles, their distributions stretching to energies ordersof magnitude higher than thermal. Another basic question is why plasma distribution function atlow energies is also non-thermal. I will offer a couple of generic mechanisms derived based on theideas we developed in turbulence, which may explain some of these basic facts.

Primary author: BERESNYAK, Andrey (Naval Research Laboratory)

Presenter: BERESNYAK, Andrey (Naval Research Laboratory)



28th Texas Symp … / Report of Contributions Tomographic lensing constraints …


Tomographic lensing constraints with galaxyclustering


We investigate how well the lensing potential can be measured tomographically with future galaxysurveys using their number counts. Such a measurement is a consistency test of the standardΛCDM framework.Based on galaxy angular-redshift power spectra, our analysis suggests that the survey can measurethe amplitude of the lensing potential at the same level of precision as other standard ΛCDMcosmological parameters. We further discuss how the lensing signal affects the angular-redshiftbispectra.

Primary author: MONTANARI, Francesco (Universite de Geneve (CH))

Presenter: MONTANARI, Francesco (Universite de Geneve (CH))



28th Texas Symp … / Report of Contributions A Palatini formalism for MOND in …


A Palatini formalism for MOND in f (χ) gravityTuesday, December 15, 2015 6:22 PM (3 minutes)

In this work we construct a relativistic extension of the MODifiedNewtonian Dynamics (MOND) in the metric formalism f(χ) using thePalatini approach. We show that a simple power law: f(χ) = χb,with b = 3/2 corresponds to the non-relativistic form of MOND.Amongst the many approaches proposed to extend MOND to a relativisticregime, the Palatini metric formalism discussed here, yields second orderfield equations, which is a desirable (but not a necessary) requirementin a gravitational theory. We briefly discuss lensing applications ofthis proposal.

Primary author: BARRIENTOS RODRÍGUEZ, Ernesto (Universidad Nacional Autónoma de Méx-ico)

Presenter: BARRIENTOS RODRÍGUEZ, Ernesto (Universidad Nacional Autónoma de México)



28th Texas Symp … / Report of Contributions Backrection of voids in a Friedman …


Backrection of voids in a Friedman background withconstant w equation of state.


I introduce new exact solutions of the Szekeres-Szafron type describing voids on a Friedmann-Roberson-Walker background with w=constant equation of state. At least in the linear regime theinhomogeneities can be thought of as large scale perturbations of the background. Using theseexact solutions the averaged quantities of the Buchert scheme can be calculated exactly. I showthat in general the late-time evolution is dominated by the voids: these back-react in such a waythat the average expansion is significantly different from the background one, I will describe how.

Primary author: BRUNI, Marco (University of Portsmouth)

Presenter: BRUNI, Marco (University of Portsmouth)



28th Texas Symp … / Report of Contributions Cold dark energy and cosmologica …


Cold dark energy and cosmological parameterestimation


Cold (or clustering) dark energy models present an interesting phenomonology in comparison tostandard homogeneous dark energy.We investigate the impact of cold dark energy on the background evolution, on the linear level,as well as at the nonlinear level on structure formation. For an accurate description at the non-linear level, the halo mass function is carefully recalibrated to include the effect of dark energyperturbations, employing the spherical collapse formalism. Using our MCMC likelihood analysisof X-ray cluster samples together with standard cosmological data sets, we constrain cosmologicalparameters when incorporating these non-linear corrections. We emphasize the impact on theconstraints of the cosmological parameters when taking into account dark energy perturbationsfor cold dark energy.

Primary author: HENEKA, Caroline (Dark Cosmology Centre, Copenhagen)

Presenter: HENEKA, Caroline (Dark Cosmology Centre, Copenhagen)



28th Texas Symp … / Report of Contributions Gravitational wave attenuation th …


Gravitational wave attenuation through interactionswith charged particles


It has been previously shown that the energy lost from an incident gravitational wave (GW) on acloud of charged particles can manifest itself an electromagnetic field, causing the GW to attenuate.Furthermore, it can be shown that the presence of the field and the circumstances in which it wasgenerated leads to currents and subsequently magnetic fields. We plan to calculate how muchenergy would be lost by a GW to the cloud of charged particles. We also plan on providing moreevidence for the idea that gravitational waves could have created the first magnetic fields in theearly universe.

Collaboration

The College of New Jersey

Primary authors: AVENOSO, Joseph (The College of New Jersey); WICKRAMASINGHE, Thulsi(The College of New Jersey); VIDUCIC, Tyler (The College of New Jersey)

Presenters: AVENOSO, Joseph (The College of New Jersey); VIDUCIC, Tyler (The College of NewJersey)



28th Texas Symp … / Report of Contributions Hot Plasma Emissions in the Ultra- …


Hot Plasma Emissions in the Ultra-compact BinaryPulsar 4U 1626-67


4U 1626-67 is an ultra-compact binary pulsar with a pulse periodof 7.7 sec and an orbital period of 40 min. Its X-ray spectrumvaries distinctively before and after torquereversal episodes. 4U 1626-67 is a peculiar ultra-compact binaryin that it not only truncates its accretion disk at the magnetosphericradius, but also emits Ne and O Doppler X-ray lines, The nature ofthese lines have remained quite mysterious but we can now show thatthese lines originate from a coronal type plasma with temperaturesup to 10 Million degrees located at the magnetospheric radius.We also observe consistent variations in the disk lines before andafter torque reversal. The observed disk lines constrain the angleof inclination to 38 degrees, which is is significally largerthan previously assumed. We discuss these findings in the contextof accreting X-ray binaries and binary pulsar properties.

Primary author: SCHULZ, Norbert S. (Massachusetts Institute of Technology)

Co-authors: CHAKRABARTY, Deepto (MIT); MARSHALL, Herman (MIT)

Presenter: SCHULZ, Norbert S. (Massachusetts Institute of Technology)



28th Texas Symp … / Report of Contributions Evolution of primordial magnetic f …


Evolution of primordial magnetic fieldsWednesday, December 16, 2015 3:03 PM (21 minutes)

There was a time when primordial magnetic fields posed a seriouscontender to explaining the origin of magnetic fields in galaxiesand on larger scales. This has changed drastically during the pastthree decades, and now the dynamo origin of galactic magnetic fields isunchallenged. Nevertheless, primordial magnetic fields might still be anattractive possibility to explaining magnetic fields between clustersof galaxies, which are difficult to get magnetized by astrophysicalmechanisms such as outflows from active galactic nuclei. Primordialmagnetic fields generated during the electroweak phase transition,for example would decay during much of their subsequent evolution,but helicity slows down the decay by inverse cascading the field tolarger scales. Dynamo-generated magnetic fields, on the other hand,also tend to be helical, if the dynamo operates in the presence ofrotation and stratification. In my talk, I will focus on the evolutionof primordial magnetic fields using numerical simulations.In the presence of magnetic helicity, inverse transfer from small tolarge scales is well known in magnetohydrodynamic (MHD) turbulence and hasapplications in astrophysics, cosmology, and fusion plasmas.Using high resolution direct numerical simulations of magneticallydominated self-similarly decaying MHD turbulence, we reporta similar inverse transfer even in the absence of magnetic helicity.We compute for the first time spectral energy transfer rates to showthat this inverse transfer is about half as strong as with helicity, butin both cases the magnetic gain at large scales results from velocityat similar scales interacting with smaller-scale magnetic fields.This suggests that both inverse transfers are a consequence ofa universal mechanisms for magnetically dominated turbulence.Possible explanations include inverse cascading of the mean squared vectorpotential associated with local near two-dimensionality and theshallower k^2 subinertial range spectrum of kinetic energyforcing the magnetic field with a k^4 subinertial rangeto attain larger-scale coherence.The inertial range shows a clear k^-2 spectrum and isthe first example of fully isotropic magnetically dominatedMHD turbulence exhibiting weak turbulence scaling.

Primary author: BRANDENBURG, Axel (Nordita)

Co-authors: Dr TEVZADZE, Alexander (Tbilisi State University); Dr KAHNIASHVILI, Tina (CarnegieMellon University)

Presenter: BRANDENBURG, Axel (Nordita)


28th Texas Symp … / Report of Contributions Evolution of primordial magnetic f …



28th Texas Symp … / Report of Contributions A relativistic metric extension of g …


A relativistic metric extension of gravity based in thedynamics and lensing of individual, groups and

clusters of galaxiesTuesday, December 15, 2015 6:13 PM (3 minutes)

A metric extension of gravity based on the Tully-Fisher law ispresented. It will be shown that the Tully-Fisher law extends from thedynamics of globular clusters up to the dynamics of groups of galaxiesand how it can be consider as a modified version of Kepler’s third law.With it, it will be shown how at second perturbation order lensing canbe fully understood and that the corresponding PPN gamma parameter isrequired to be close to one. I will show how to construct a relativisticmetric extension of gravity using this observational facts and brieflymention its potential for understanding the dynamics of clusters ofgalaxies and of the expanding universe without the need to introduceany dark matter/energy entities for its description.

Primary author: Dr MENDOZA, Sergio (Instituto de Astronomia, Universidad Nacional Autonomade Mexico (UNAM))

Presenter: Dr MENDOZA, Sergio (Instituto de Astronomia, Universidad Nacional Autonoma deMexico (UNAM))



28th Texas Symp … / Report of Contributions An eclipsing binary black hole in …


An eclipsing binary black hole in MRK 421Tuesday, December 15, 2015 6:23 PM (3 minutes)

A model independent power spectrum light curve analysis in the optical,hard X-ray and gamma-rays of the blazar MRK 421 shows clear evidencefor a periodicity of approximately 400 days. A subsequent full maximumlikelihood analysis fitting an eclipse model confirms this periodicitywith a consistent phase for the bands analysed. The most parsimoniousphysical mechanism to which this periodicity could be ascribed is adynamical effect produced by an orbiting supermassive black hole companionof mass of about 10^7 solar masses eclipsing the central black hole,which has an approximate mass of 10^8 solar masses.

Primary authors: Dr BENITEZ, Erika (Instituto de Astronomia, Universidad Nacional Autonomade Mexico (UNAM)); Dr MENDOZA, Sergio (Instituto de Astronomia, Universidad Nacional Autonomade Mexico)

Presenters: Dr BENITEZ, Erika (Instituto de Astronomia, Universidad Nacional Autonoma de Mex-ico (UNAM)); Dr MENDOZA, Sergio (Instituto de Astronomia, Universidad Nacional Autonoma deMexico)



28th Texas Symp … / Report of Contributions High redshift BAO from BOSS to e …


High redshift BAO from BOSS to eBOSSMonday, December 14, 2015 2:00 PM (27 minutes)

The first detection of Baryon Acoustic Oscillations (BAO) in the correlation function of the galaxydensity field by Eisenstein et al. (2005) and Cole et al. (2005) set a milestone in the era of precisioncosmology, providing a new, independent method for the measurement of cosmological distances.The Baryon Oscillation Spectroscopic Survey (BOSS), one of the experiment of the third generationof the Sloan Digital Sky Survey (SDSS-III), produced the first high redshift (z=2.34) measurementof the BAO scale using the Lyman-alpha forest of quasars as a tracer of the underlying matterdensity field (Delubac et al. 2015). During this talk, I will review the analysis that led to thismeasurement as well as present new results using the final dataset of BOSS. I will present thecosmological implications of this measurement when combined with other results (Aubourg et al.2015) including constraints on the Dark Energy. I will pursue by introducing the extended BaryonOscillation Spectroscopic Survey (eBOSS) of the fourth generation of the SDSS (SDSS-IV) that usesthe same facility as BOSS, and show how it will tighten the constraints on our cosmological model.

Collaboration

BOSS and eBOSS collaborations

Primary author: Dr DELUBAC, Timothée (Ecole Polytechnique Fédérale de Lausanne)

Presenter: Dr DELUBAC, Timothée (Ecole Polytechnique Fédérale de Lausanne)



28th Texas Symp … / Report of Contributions The gamma-ray monitoring of ne …


The gamma-ray monitoring of newly discoveredBe/BH binary system MWC 656


MWC 656 is a Be star with a black hole (BH) companion, being the first and unique Be/BH binarysystem found. The detected X-ray counterpart implies that MWC 656 is, as well, the first Be/BHX-ray binary found. We carried out a search in archival AGILE data and found ten gamma-rayflares compatible with the position of the binary system, although no periodicity in the gamma-rayactivity has been detected, so far. We report on the spectral fitting for both X-ray and gamma-raydata. The derived non-thermal X-ray luminosity of the system, together with radio luminosityupper limits, makes MWC 656 compatible with the radio/X-ray luminosity correlation found forLMXBs. MWC 656 is located at the level of the faintest detected LMXBs, thus suggesting that thiscorrelation might also be valid for HMXBs with very low X-ray luminosities.

Primary author: SABATINI, Sabina (National Institute for Astrophysics - INAF)

Presenter: MUNAR-ADROVER, Pere (INAF-IAPS)



28th Texas Symp … / Report of Contributions Precision measurement of the local …


Precision measurement of the local bias of darkmatter halos


The large-scale local bias parameters of dark matter halos are essential to describe the statisticsof halos and galaxies on large scales, as well as for the halo model of the matter distribution. Werecently obtained precise measurements of the three leading bias parameters from simulationsusing a novel technique : the separate universe simulations. For b_2 and b_3, these are the mostprecise measurements to date. We compare our results with bias parameters obtained from twoand three points cross-correlation functions and with theoretical predictions from the excursion setpeaks (ESP) model. For b_1, we get agreement at percent level with the correlations measurementsand at 5% level with the ESP. This plus the very good agreement also found for the other biasparameters confirms the validity of the method and its efficiency.

In a separate project, we also report on new simulation results on the scale-dependent bias onprimordial non-Gaussianity.

Primary author: LAZEYRAS, Titouan (MPA)

Presenter: LAZEYRAS, Titouan (MPA)



28th Texas Symp … / Report of Contributions First numerical simulations of the …


First numerical simulations of the chiral MHDdynamo effect


Under extreme conditions, e.g. at high temperatures like in the early Universe, the usual magne-tohydrodynamical (MHD) equations need to be extended. The origin of the modification is theasymmetry of the chemical potential of right- and left-handed fermions. To describe the evolutionof a plasma, additional terms as well as new equations for the chiral chemical potential have tobe included. We have implemented these extensions in the Pencil Code, which is a high-orderfinite-difference code developed for solving compressible MHD. We study laminar dynamos andfind an exponential increase of the magnetic energy with the growth rate depending on the chem-ical potential. We further analyze the evolution of magnetic fields in the presence of turbulence.Potentially, chirality has interesting effects on the properties of magnetic fields in the early Uni-verse and in particular on the evolution of magnetic helicity which is directly coupled to the chiralchemical potential.

Primary author: SCHOBER, Jennifer

Co-authors: BOYARSKY, Alexey (CERN); BRANDENBURG, Axel (Nordita); ROGACHEVSKII, Igor(Ben Gurion University of the Negev); RUCHAYSKIY, Oleg (Ecole Polytechnique Federale de Lausanne(CH))

Presenter: SCHOBER, Jennifer



28th Texas Symp … / Report of Contributions Primordial Magnetism in CMB


Primordial Magnetism in CMBTuesday, December 15, 2015 4:55 PM (20 minutes)

I will discuss CMB signatures of primordial magnetic fields, some of the existing constraints, andwhat can be expected from future CMB experiments.

Primary author: Dr POGOSIAN, Levon (Simon Fraser University)

Presenter: Dr POGOSIAN, Levon (Simon Fraser University)



28th Texas Symp … / Report of Contributions A curved jet model for the synchro …


A curved jet model for the synchrotron emission ofthe BL Lac object PG 1553+113.


We report on the results of a multifrequency campaign on the BL Lac object PG 1553+113 that wasorganized by the Whole Earth Blazar Telescope (WEBT) Collaboration in 2013 April-August. Nine-teen optical, two near-IR, and three radio telescopes monitored the source to follow its behaviourat low energies during and around the high-energy observations by the MAGIC telescopes in April-July. A general bluer-when-brighter trend characterizes the optical emission.We also analyse the UV and X-ray data acquired by the Swift and XMM-Newton satellites in thesame period and compare them with previous observations.The long XMM-Newton exposure reveals a curved X-ray spectrum, which shows a harder-when-brighter behaviour on long time scales.In the spectral energy distribution (SED), the XMM-Newton near-UV spectrum is hard, while Swiftdata display a softer shape that is confirmed by previous HST-COS and IUE observations.An estimate of the synchrotron peak through polynomial fits to the optical-X-ray SED suggeststhat it lies in the 4-30 eV energy range, with a general increase with X-ray brightness.However, the UV and X-ray spectra do not connect smoothly. We propose an interpretation of theSED shape and variability in terms of orientation changes of the helical structure of an inhomoge-neous jet.

Collaboration

The Whole Earth Blazar Telescope (WEBT) Collaboration

Primary authors: Dr STAMERRA, Antonio (INAF-Osservatorio Astrofisico di Torino, Italy); DrRAITERI, Claudia M. (INAF-Osservatorio Astrofisico di Torino, Italy); Dr VILLATA, Massimo (IN-AF-Osservatorio Astrofisico di Torino)

Presenter: Dr STAMERRA, Antonio (INAF-Osservatorio Astrofisico di Torino, Italy)



28th Texas Symp … / Report of Contributions Dark energy as a fixed point of the …


Dark energy as a fixed point of the EinsteinYang-Mills Higgs Equations


We study the Einstein Yang-Mills Higgs equations in the SO(3) representation on a isotropic andhomogeneous flat Universe, in the presence of radiation and matter fluids. We map the equationsof motion into an autonomous dynamical system of first-order differential equations and we findthe equilibrium points. We show that there is only one stable fixed point that corresponds to anaccelerated expanding Universe in the future. In the past, instead, there is an unstable fixed pointthat implies a stiff-matter domination. In between, we find three other unstable fixed points, corre-sponding, in chronological order, to radiation domination, to matter domination, and, finally, to atransition from decelerated expansion to accelerated expansion. We solve the system numericallyand we confirm that there are smooth trajectories that correctly describe the evolution of the Uni-verse, from a remote past dominated by radiation to a remote future dominated by dark energy,passing through a matter-dominated phase.

Primary author: RINALDI, Massimiliano (University of Trento)

Presenter: RINALDI, Massimiliano (University of Trento)



28th Texas Symp … / Report of Contributions Galactic magnetic field and uncon- …


Galactic magnetic field and uncon-ventional cosmicray propagation


Fermi-LAT, PAMELA, AMS-02, Planck and IceCube are providing us with impressive multimes-senger pictures of our Galaxy. The diffuse components of those emissions are commonly modeledassuming uniform cosmic ray (CR) transport properties. Such an approach, however, is not moti-vated neither by theoretical nor observational arguments. I will show that relaxing the uniformCR propagation assumption it allows to explain several anomalies including the excess of gamma-rays observed by Milagro and Fermi-LAT in the inner Galactic plane and part of the high-energyneutrino emission measured by IceCube.I will argue as such a behaviour may be explained under quite reasonable conditions of the regularand turbulent components of the Galactic magnetic field.

Primary author: GRASSO, Dario (INFN)

Presenter: GRASSO, Dario (INFN)



28th Texas Symp … / Report of Contributions The Cosmic Laboratory: Probing I …


The Cosmic Laboratory: Probing Inflation withGalaxy Clustering


The large-scale distribution of galaxies is a powerful probe of the physics of Inflation. In this talk,I will explain what it would take for a future galaxy survey to use galaxies as a probe of primordialnon-Gaussianity in order to distinguish between single-field and multi-field Inflation, and I willintroduce a specific proposal for such a survey, called SPHEREx. I will also revisit the predictionfor the exact level of non-Gaussianity and scale-dependent bias in single-field Inflation.

Primary author: DE PUTTER, Roland

Presenter: DE PUTTER, Roland



28th Texas Symp … / Report of Contributions CMB temperature and polarisation …


CMB temperature and polarisation anisotropies: agoldmine for cosmology.


Over the last two decades cosmic microwave background (CMB) anisotropies have revolutionisedour view of cosmology. Generations of experiments have successively uncovered the amplitudeof the temperature fluctuations at large scales, the existence of acoustic peaks in both tempera-ture and polarisation and the small scale damping. These observations have now established aminimal cosmological model with unprecedented accuracy of its cosmological parameters. I willshow how CMB temperature and polarisation anisotropies are powerful cosmological probes ofthe concordance model.

Primary author: AGHANIM, Nabila (Universite Paris Sud)

Presenter: AGHANIM, Nabila (Universite Paris Sud)



28th Texas Symp … / Report of Contributions Galactic Science with the Cherenk …


Galactic Science with the Cherenkov Telescope ArrayMonday, December 14, 2015 2:20 PM (25 minutes)

CTA is the next generation ground based gamma-ray observatory planned to start operationsbefore the end of the decade. With tens of telescopes on sites in both hemispheres, it will allowprobing the Milky Way with an unprecedented sensitivity and angular resolution, in the energydomain from a few tens of GeV to a few hundreds of TeV. I will review the CTA Galactic scienceprogram ranging from the Galaxy plane to the LMC surveys, including selected deep field studies,transients monitoring and the long standing search for pevatrons.

Collaboration

CTA

Primary author: Dr STOLARCZYK, Thierry (IRFU/SAp,CEA Saclay, 91190 Gif-sur-Yvette (FR))

Presenter: Dr STOLARCZYK, Thierry (IRFU/SAp,CEA Saclay, 91190 Gif-sur-Yvette (FR))



28th Texas Symp … / Report of Contributions The Galactic Center - a unique lab …


The Galactic Center - a unique laboratory forrelativity


Located at 8kpc only, the Galactic Center allows studying a galactic nucleus in unparalleled detail.With the advent of high-resolution, near-infrared instrumentation in the last decade it becamepossible to follow individual stellar orbits around the radio source Sgr Awith orbital periodsas short as 12 years. The orbits determine the mass of Sgr A to 4 million solar masses,and thus provide compelling evidence for the massive black hole paradigm. Also, variable flareemission originating from the direct vicinity of the event horizon has been discovered.The next generationnear-infrared instrument GRAVITY aims at increasing the resolution furtherby interferometrrcially combining the light of the four telescopes of the VLT. The resolutionachievable is of order 3 milli-arcsec and will allow monitoring stellar orbits with orbital periodsof 1 year only. The relativistic prograde periastron precession gets then accessible astrometrically.The astrometric accuracy of GRAVITY is of order of the event horizon size of Sgr A. This meansthat we might be able to measure the orbital motion of the flaring emission, and thus that wemight have access to measuring the spin of Sgr A.

Primary authors: Dr EISENHAUER, Franck (Max Planck Inst. fur Extraterrestrische Physik); GILLESSEN,Stefan (Max Planck Inst fur Extraterrestrische Physik)

Presenter: GILLESSEN, Stefan (Max Planck Inst fur Extraterrestrische Physik)



28th Texas Symp … / Report of Contributions On homogeneous and isotropic un …


On homogeneous and isotropic universeMonday, December 14, 2015 4:35 PM (20 minutes)

We give a simple example of space-time metric, illustrating that homogeneity and isotropy of spaceslices at all moments of time is not obligatory lifted to a full system of six Killing vector fields inspace-time, thus it cannot be interpreted as a symmetry of a four dimensional metric. The metricdepends on two arbitrary and independent functions of time. One of these functions is the usualscale factor. The second function cannot be removed by coordinate transformations. We provethat it must be equal to zero, if the metric satisfies Einstein’s equations and the matter energymomentum tensor is homogeneous and isotropic. A new, equivalent, definition of homogeneousand isotropic space-time is given.

Primary author: KATANAEV, Mikhail (Steklov Mathematical Institute, Moscow)

Presenter: KATANAEV, Mikhail (Steklov Mathematical Institute, Moscow)



28th Texas Symp … / Report of Contributions Novel Approaches for the Analysis …


Novel Approaches for the Analysis of ExtragalacticMagnetic Fields


In order to give a consistent picture of cosmic, i.e. galactic and extragalactic, magnetic fields, dif-ferent approaches are possible and often even necessary. Here we present three of them: First, asemianalytic analysis of the time evolution of primordial magnetic fields from which their prop-erties and, subsequently, the nature of present-day intergalactic magnetic fields may be deduced.Second, the use of high-performance computing infrastructure by developing powerful algorithmsfor (magneto-)hydrodynamic simulations and applying them to astrophysical problems. We arecurrently developing a code which applies kinetic schemes in massive parallel computing on highperformance multiprocessor systems in a new way to calculate both hydro- and electrodynamicquantities. Finally, as a third approach, astroparticle physics might be used as magnetic fields leaveimprints of their properties on charged particles transversing them. Here we focus on electromag-netic cascades by developing a software based on CRPropa which simulates the propagation ofparticles from such cascades through the intergalactic medium in three dimensions. This may inparticular be used to obtain information about the helicity of extragalactic magnetic fields.

Primary author: Dr SAVELIEV, Andrey (University of Hamburg/Keldysh Institute)

Presenter: Dr SAVELIEV, Andrey (University of Hamburg/Keldysh Institute)



28th Texas Symp … / Report of Contributions Extragalactic science with the Che …


Extragalactic science with the Cherenkov TelescopeArray


The Cherenkov Telescope Array (CTA) is the next-generation observatory for ground-based gamma-ray astronomy. A Key Science Program (KSP) of observations will be conducted, providing legacydata sets of benefit to the entire astronomical community. This contribution presents the extra-galactic science addressed in the CTA KSP. The objectives contain targeted observations of activegalactic nuclei, galaxy clusters and star-forming galaxies as well as follow-up observations ofgamma-ray bursts and other transients triggered by multi-messenger alerts. The KSP also includesa survey of one quarter of the extra-galactic sky, permitting a thorough search for cosmic particleaccelerators and the exploration of the unknown.

Collaboration

for the CTA Consortium

Primary author: GERARD, Lucie

Presenter: GERARD, Lucie



28th Texas Symp … / Report of Contributions Space astrometry with Gaia and re …


Space astrometry with Gaia and relativisticastrophysics


Esa’s second space astrometry mission Gaia was launched in December 2013 and after an extendedcommissioning period started its scientific operations in July 2014. After 17 months of observationsGaia delivered an immense dataset of high-accuracy positional observations. In spite of someunexpected difficulties with the instrument, Gaia Data Processing and Analysis Consortium isprogressing well towards first data releases scheduled for 2016.

This presentation will review the promises and challenges of Gaia space astrometry in the field ofrelativistic astrophysics. Potential applications of Gaia astrometry in this field range from weak-field tests of general relativity in the gravitational field of solar system to estimates of energyflux for gravitational wave background in a certain frequency domain. Space astrometry can alsobe used to provide model-independent estimates of the masses of invisible components in someknown compact binary systems. The review of these Gaia promises will be accompanied by acritical analysis of the actual performance of the instrument.

Collaboration

Gaia Data Processing and Analysis Consortium

Primary author: Prof. KLIONER, Sergei (Lohrmann Observatorium, Technische Universitaet Dres-den)

Presenter: Prof. KLIONER, Sergei (Lohrmann Observatorium, Technische Universitaet Dresden)



28th Texas Symp … / Report of Contributions Dark matter and fundamental phy …


Dark matter and fundamental physics with theCherenkov Telescope Array


The Cherenkov Telescope Array (CTA) is a worldwide project aiming at building the next groundbased gamma-ray observatory with a sensitivity ten times better than current experiments likeH.E.S.S., MAGIC and VERITAS. CTA will be composed of several tens of telescopes with differentsizes distributed on two sites located in the northern and southern hemispheres. CTA will also havea much wider energy coverage and improved angular resolution. The presentation will describethe science program on dark matter and fundamental physics.

Collaboration

CTA consortium

Primary author: MOULIN, Emmanuel (CEA Saclay)

Presenter: MOULIN, Emmanuel (CEA Saclay)



28th Texas Symp … / Report of Contributions Millisecond pulsars: on their own, …


Millisecond pulsars: on their own, with a friend, oreven twoWednesday, December 16, 2015 2:00 PM (30 minutes)

As the most rapidly rotating stars known, millisecond pulsars continueto enjoy great scientific interest and broad impact. They acquiretheir millisecond rotational periods through mass transfer from abinary stellar companion; via their radio, X-ray and/or gamma-raypulsations we can precisely time their spin rate and orbital motionaround a companion object (or even multiple companions). Millisecondpulsars are thus not only exotic stars in their own right, but alsoprecision astronomical clocks for measuring other physical effects inextreme environments. In this review talk, I will discuss how thelarge recent increase in known millisecond pulsars is shaping ourunderstanding of their formation/evolution and is enabling ever moreconstraining tests of gravitational theories and dense matter physics.

Primary author: Dr HESSELS, Jason (University of Amsterdam)

Presenter: Dr HESSELS, Jason (University of Amsterdam)



28th Texas Symp … / Report of Contributions Constraining non-standard neutri …


Constraining non-standard neutrino scenarios withPlanck 2015


Cosmological observations represent a powerful tool to constrain neutrino physics. In particu-lar, observations of the temperature and polarization anisotropies of the cosmic microwave back-ground (CMB) have the potential to constrain the properties of relic neutrinos, and possibly ofadditional light relic particles in the Universe. Even if all current cosmological data are well inagreement with the standard scenario of just three active neutrinos with negligible masses, inter-acting only through the weak force, and having an equilibrium spectrum with vanishing chemicalpotential, nevertheless deviations from this simple scenario are possible. For example, “hidden”(i.e. beyond the standard model of particle physics) neutrino interactions, mediated by a scalarparticle like the Majoron, could exist and affect the evolution of cosmic relic neutrinos. Anotherpossibility is that neutrinos do not have an equilibrium distribution, like e.g. in scenarios witha low reheating temperature. In my talk I will discuss constraints on these deviations from thestandard scenario that can be obtained using the recently released data from the Planck satellite,possibly in combination with other astrophysical and cosmological probes.

Primary author: LATTANZI, Massimiliano (University of Ferrara)

Presenter: LATTANZI, Massimiliano (University of Ferrara)



28th Texas Symp … / Report of Contributions Lessons on massive black hole bin …


Lessons on massive black hole binaries from pulsartiming arrays


Pulsar timing arrays (PTAs) are dramatically improving their sensitivity. Current upper limits startto be in tension with vanilla models of gravitational wave driven, circular supermassive black holebinaries (SMBHBs), although nothing can be safely ruled out yet. I will discuss how we can usecurrent and future PTA limits to investigate the nature of SMBHBs and learn about their overallcosmic population and the dynamics bringing them to the final gravitational wave driven merger.

Primary author: Dr SESANA, Alberto (University of Birmingham)

Presenter: Dr SESANA, Alberto (University of Birmingham)



28th Texas Symp … / Report of Contributions Planck 2015 results on Dark Energ …


Planck 2015 results on Dark Energy and ModifiedGravity


The latest cosmic microwave background data obtained by ESA Planck satellite allow us to test theevolution and content of the Universe in great detail. I will review the analysis done by the Planckcollaboration and presented in the “Planck 2015 results. XIV. Dark energy and modified gravity”paper, which considered two broad cases: a DE which affects the background evolution and DE orMG parametrizations which instead modify the evolution of cosmological perturbations. In thistalk I will also discuss the combination of Planck data with external datasets and their implicationon the constraints.

Collaboration

Planck Collaboration

Primary author: MARTINELLI, Matteo (ITP, Heidelberg)

Presenter: MARTINELLI, Matteo (ITP, Heidelberg)



28th Texas Symp … / Report of Contributions Preheating after hilltop inflation


Preheating after hilltop inflationMonday, December 14, 2015 5:15 PM (20 minutes)

During hilltop inflation, the inflaton rolls away from the maximum of its potential and towards theminimum where the universe reheats. The first stage of reheating, preheating, is non-perturbativeand, in this model, localized oscillating bubbles of the inflaton field, called oscillons, are formed.Furthermore, when other fields are present, they can be produced via a parametric resonance withthe non-homogeneous inflaton field.In this talk, I will discuss lattice simulations of the evolution of oscillons, how they are affected bythe resonance with another field and their effect on the expansion history of the universe.

Primary author: ORANI, Stefano (Basel University)

Co-authors: Mr NOLDE, David (University of Basel); CEFALÀ, Francesco (University of Basel); AN-TUSCH, Stefan (University of Basel)

Presenter: ORANI, Stefano (Basel University)



28th Texas Symp … / Report of Contributions Unveiling the parent population of …


Unveiling the parent population of beamednarrow-line Seyfert 1s


Narrow-line Seyfert 1 galaxies (NLS1s) are active galactic nuclei (AGN) recently identified as a newclass of γ-ray sources. The high energy emission is explained with the presence of a relativistic jetobserved at small angles, just like in the two classes of blazars. When the latters are observed atlarger angles they appear as radio-galaxies, but an analogue parent population for beamed NLS1shas not been determined yet. In this work we analysed this problem by studying the physical prop-erties of three different samples of parent sources candidates: steep-spectrum radio-loud NLS1s,radio-quiet NLS1s and disk-hosted radio-galaxies. In our approach we first derived black holemass and Eddington ratio from the optical spectra, then we investigated the interaction betweenthe jet and the narrow-line region from the [O III] λλ 4959,5007 lines. Finally, the radio luminosityfunction allowed us to compare their jet luminosity and hence determine the relations betweenthe samples.

Primary author: BERTON, Marco (University of Padova - Department of Physics and Astronomy”G. Galilei”)

Co-authors: Dr FOSCHINI, Luigi (National Institute for Astrophysics - INAF); Dr CIROI, Stefano(University of Padova)

Presenter: BERTON, Marco (University of Padova - Department of Physics and Astronomy ”G.Galilei”)



28th Texas Symp … / Report of Contributions QPOs and Lense-Thirring precession


QPOs and Lense-Thirring precessionThursday, December 17, 2015 3:06 PM (3 minutes)

Observations of QPOs from neutron stars and black holes suggest they must be a feature of theaccretion disc surrounding these objects. Their measured frequencies indicate they are from theinner disc, where effects from the Lense-Thirring precession are significant. However, because theproperties of the high and low frequency QPOs are so different, it is thought that separate physicalprocesses cause them. We present 3D global simulations of inclined accretion discs and identifyfeatures caused by Lense-Thirring precession that may explain both high and low frequency QPOs.We estimate the powerspectra from these simulations and compare these to observations of QPOs.

Primary author: NEALON, Rebecca (Monash University)

Presenter: NEALON, Rebecca (Monash University)



28th Texas Symp … / Report of Contributions Highlights on massive winds from …


Highlights on massive winds from AGNWednesday, December 16, 2015 2:00 PM (22 minutes)

I will briefly review the evidence for high-velocity (mildly relativistic) and massive winds in ActiveGalactic Nuclei. I will then highlight some new recent results obtained in X-rays (mostly usingdeep XMM and Chandra observations) and at multi-frequencies for both low-z AGNs and high-zQSOs. Among other things, these studies indicate that massive, high-velocity, outflows may bemore common than previously thought.

Collaboration

INAF/IASF-Bologna

Primary author: CAPPI, Massimo (National Institute for Astrophysics - INAF)

Presenter: CAPPI, Massimo (National Institute for Astrophysics - INAF)



28th Texas Symp … / Report of Contributions Gravitational waves from binary s …


Gravitational waves from binary supermassive blackholes missing in pulsar observations


Gravitational waves are expected to be radiated by supermassive black hole binaries formed duringgalaxy mergers. A stochastic superposition of gravitational waves from all such binary systemswill modulate the arrival times of pulses from radio pulsars. Using observations of millisecondpulsars obtained with the Parkes radio telescope, we constrain the characteristic amplitude of thisbackground,Ac,yr, to be < 1.0×10−15 with 95% confidence. This limit excludes predicted ranges forAc,yr from current models with 91-99.7% probability. We conclude that binary evolution is eitherstalled or dramatically accelerated by galactic-center environments, and that higher-cadence andshorter-wavelength observations would result in an increased sensitivity to gravitational waves.

Collaboration

Parkes Pulsar Timing Array

Primary author: Dr SHANNON, Ryan (CASS)

Co-author: Dr OSLOWSKI, Stefan (Bielefeld University / MPIfR Bonn)

Presenter: Dr OSLOWSKI, Stefan (Bielefeld University / MPIfR Bonn)

28th Texas Symp … / Report of Contributions The e-ASTROGAM mission


The e-ASTROGAM missionThursday, December 17, 2015 2:24 PM (19 minutes)

e-ASTROGAM is a gamma-ray observatory to be proposed as a Medium-size mission for the ESAscience program. It is dedicated to the observation of the Universe with unprecedented sensitivityin the energy range 0.3 – 100 MeV extending up to GeV energies, together with a ground-breakingpolarization capability. In this energy window, a variety of phenomena and sources await theirdiscovery and many foundational questions can be answered. The e-ASTROGAM core science isfocused on (1) the mysteries of the Galactic centre and inner Galaxy, including the supermassiveblack hole activity, the Fermi Bubbles, the origin of the Galactic positrons, and dark matter sig-natures in a new energy window; (2) nucleosynthesis and propagation of heavy elements in ourGalaxy and beyond; (3) activity from extreme particle accelerators, including disk-jet transitions inactive galactic nuclei and the origin of the extragalactic gamma-ray background. e-ASTROGAMwill be uniquely complementary to a variety of ground and space observatories ranging from ra-dio, optical, X-ray and TeV energies, as well as to neutrino and gravitational wave detectors. Thee-ASTROGAM payload consists of a single instrument for the simultaneous detection of Comp-ton and pair-producing gamma-ray events. It is based on a very high TRL for all subsystems andincludes many innovative features for the main detectors and associated electronics.

Collaboration

ASTROGAM Collaboration

Primary author: TATISCHEFF, Vincent (CSNSM, CNRS)

Presenter: TATISCHEFF, Vincent (CSNSM, CNRS)



28th Texas Symp … / Report of Contributions The Plasma Physics of TeV Blazars


The Plasma Physics of TeV BlazarsTuesday, December 15, 2015 3:25 PM (20 minutes)

Constraints on the primordial intergalactic magnetic field from thenon-observation of inverse Compton cascades around extragalactic veryhigh energy sources, i.e., the TeV blazars, assume that inverseCompton scattering is the dominant physical mechanism by which diluteultrarelativistic pair beams lose their energy. Over the last fewyears, we have considered the effect of plasma instabilities on theseultrarelativistic beams. We argue that the linear growth rate ofthese instabilities, and in particular the oblique instability, are sofast that these instabilites may dominate the cooling of these pairbeams leading to an order of magnitude or more suppression in theinverse Compton cascade. We review the relevant physics of theseplasma instabilities and discuss the linear instability of these pairbeams. We also discuss recent work on the various nonlinear aspectsof this instability and the effect of density gradients on theinstability. We highlight the effect of this instability on theconstraints of the intergalactic magnetic field, arguing that theseconstraints are precluded in the presences of these instabilities. Wealso discuss the implication of these instabilities on the populationof TeV blazars, and the intergalactic gamma ray background. Finally,we close with a discussion on the effect of these extra blazar heatingon cosmological structure formation, in particular, thetemperature-overdensity profile and the Lyman-alpha forest.

Primary authors: Dr LAMBERTS, Astrid (California Institute of Technology); Prof. BRODERICK,Avery (Perimeter Institute and University of Waterloo); Dr PFROMMER, Christoph (HITS); Dr PUCH-WEIN, Ewald (University of Cambridge); Mr SHALABY, Mohamad (University of Waterloo); CHANG,Philip

Presenter: CHANG, Philip



28th Texas Symp … / Report of Contributions Constraining the energy scale of c …


Constraining the energy scale of cosmic strings withPTAsThursday, December 17, 2015 6:03 PM (22 minutes)

Pulsar Timing Arrays observe a set of millisecond pulsars at high timing precision over long pe-riods of time, aiming to directly detect gravitational waves. Probing the nHz frequency regime,PTAs are sensitive also to many primordial GW sources, with one of them being cosmic strings; aweb of string-like energy concentrations that may have formed right after Inflation and permeatesthe Universe. In this talk, I will give a brief introduction to these exotic sources, describe why theyare so interesting from a cosmological perspective, and show that PTAs is the best tool currentlyavailable for the detection of their GW signatures. Since current PTA projects have only managedto set upper limits on the amplitude of a potential SGWB, I will show how these limits can betranslated to limits of the energy scale, or tension in other words, of cosmic strings. In particular, Iwill present the latest upper limits on the string tension by the EPTA and NANOGrav. The genericway in which these limits have been computed, grant them robustness close to those computed byCMB data, and for the first time, such PTA results have reached and surpassed, the best availableCMB-originating tension limits from Planck.

Collaboration

EPTA (and NANOGrav)

Primary author: Dr SANIDAS, Sotiris (University of Amsterdam)

Co-authors: Prof. STAPPERS, Ben (University of Manchester); Prof. BATTYE, Richard (Universityof Manchester)

Presenter: Dr SANIDAS, Sotiris (University of Amsterdam)



28th Texas Symp … / Report of Contributions Making waves: modeling gravitati …


Making waves: modeling gravitational waves fromcoalescing binary systems


Gravitational waves were first predicted by Albert Einstein in 1916 on thebasis of his theory of general relativity. In the next five years ground-basedinterferometers, such as advanced LIGO, advanced Virgo and KAGRA, are likelyto provide the first direct detections of gravitational waves from binary systems composedof black holes and/or neutron stars. In this talk, we review the progress done over thelast several years at developing accurate signal models for the searches, so that wecan take full advantage of the discovery potential of the detectors. We also discuss theunique astrophysical and fundamental physics information that we will be able toextract upon detection.

Primary author: Prof. BUONANNO, Alessandra (Max Planck Institute for Gravitational Physics)

Presenter: Prof. BUONANNO, Alessandra (Max Planck Institute for Gravitational Physics)



28th Texas Symp … / Report of Contributions Quasi-Periodic Oscillations are mo …


Quasi-Periodic Oscillations are more than justfrequencies


Quasi-periodic oscillations (QPO) are an important probe of the timing properties of black-holebinaries and a ubiquitous feature of their PDS. For that reason, many attempts to explain theirorigin have also reduced them to their frequencies. In order to explore their behavior beyond this,we consider three simple classes of models: elongated hot spots, tori and spirals. We perturb theequilibrium temperature of a thin disk to create these structures. The perturbed disk is supposedto emit blackbody radiation at the local temperature. Radiation is ray-traced in the Schwarzschildmetric to a distant observer.We then studied different timing AND spectral features of those models, such as the impact ofinclination, how the rms evolves with frequencies, and the impact on the spectral fit; showinghow characteristics beyond the frequency could be used to differentiate between models.

Primary author: VARNIERE, Peggy (CNRS)

Co-author: VINCENT, Frederic (Observatoire de Paris)

Presenter: VINCENT, Frederic (Observatoire de Paris)



28th Texas Symp … / Report of Contributions Modelling inhomogeneous cosmol …


Modelling inhomogeneous cosmologies withNumerical Relativity


Building accurate, multi-scale models of the Universe is a complex but necessary task in the eraof precision cosmology, when observational data demands a thorough understanding of all effectswhich are expected to contribute at the 1% level, among which the full role of General Relativity.This task has recently been tackled with a variety of approaches, which range from the studyof toy models [1], to analytical expansions [2] and hybrid analytical-numerical methods whererelativistic effects are superimposed on classical, Newtonian N-body systems [3][4][5].

In this presentation, I will describe recent work carried out in Numerical Relativity to describe therelativistic Universe exactly, integrating Einstein’s equation in three dimensions. This approach isthe only one that can account for the full extent of the theory, and has already yielded significantresults in several scenarios, such as black-hole lattices [6] and scalar-field collapse in cosmologicalsettings [7].

References:

[1] Korzyński, M., “Nonlinear effects of general relativity from multiscale structure”, http://arxiv.org/abs/1412.3865

[2] Bruneton J.-P. and Larena, J., “Dynamics of a lattice Universe: The dust approximation in cos-mology”, http://arxiv.org/abs/1204.3433

[3] Bruni, M., Thomas, D. and Wands, D., “Computing General Relativistic effects from NewtonianN-body simulations: Frame dragging in the post-Friedmann approach”, http://arxiv.org/abs/1306.1562

[4] Adamek, J. et al, “N-body methods for relativistic cosmology”, http://arxiv.org/abs/1408.3352

[5] Adamek, J. et al, “General relativity and cosmic structure formation”, http://arxiv.org/abs/1509.01699

[6] Bentivegna, E. and Korzynski, M., “Evolution of a periodic eight-black-hole lattice in numericalrelativity”, http://arxiv.org/abs/1204.3568

[7] Torres, J. M. et al, “Cosmological nonlinear structure formation in full general relativity”,http://arxiv.org/abs/1409.7953

Primary author: Dr BENTIVEGNA, Eloisa (Università degli Studi di Catania)

Presenter: Dr BENTIVEGNA, Eloisa (Università degli Studi di Catania)



28th Texas Symp … / Report of Contributions Quantum vacuum as the cause of …


Quantum vacuum as the cause of the phenomenausually attributed to dark matter


We show that if quantum vacuum fluctuations are virtual gravitational dipoles, then the phenom-ena usually attributed to hypothetical dark matter, may be considered as a consequence of thegravitational polarization of the quantum vacuum by the immersed baryonic matter; apparently,at least mathematically, the galactic halo of dark matter can be replaced by the halo of the polarizedquantum vacuum.The eventual gravitational effects of the quantum vacuum “enriched” with vir-tual gravitational dipoles, can be revealed by the study of orbits of tiny satellites in trans-Neptunianbinaries (for instance UX 25 and Eris-Dysnomia).

Primary author: HAJDUKOVIC, Dragan (Institute of Physics, Astrophysics and Cosmology (ME))

Presenter: HAJDUKOVIC, Dragan (Institute of Physics, Astrophysics and Cosmology (ME))



28th Texas Symp … / Report of Contributions The Crab pulsar: Examining its pr …


The Crab pulsar: Examining its profile and derivinghigh precision X-ray ephemerides


We present here the results of an analysis of 15 years of regular XMM-Newton EPIC pn obser-vations of the Crab pulsar. The analysis of its pulse profile is based on a multi-harmonic decom-position using a new periodogram statistic which is ideally suited for studying the details of thecharacteristics of peaked pulse profiles such as the Crab’s, especially in time-tagged event data.The decomposition and generalised modified Rayleigh statistic are both applied and presentedhere for the first time. Their application is extended to study the time-dependent evolution of thepulsar’s emission over this 15 year period and 70 individual observations to derive high precisionephemerides based solely on the X-ray data.

Primary author: BELANGER, Guillaume (ESA)

Presenter: BELANGER, Guillaume (ESA)



28th Texas Symp … / Report of Contributions Creation of Emergent Universe wi …


Creation of Emergent Universe with WormholesMonday, December 14, 2015 2:21 PM (21 minutes)

Emergent universe (EU) scenarios describe the evolution of a static Einstein universe in the infinitepast whereby certain problems associated with the big-bang singularity can be circumvented. Aflat universe composed of interacting fluids with a non-linear equation of state within the EU sce-nario leads to a viable cosmological model accommodating the presently observed accelerating era,as well. In the present work we focus on the origin of such a EU scenario. By investigating the veryearly universe in the presence of gravitational instanton solutions, we show how a static Einsteinuniverse emerges, leading to a cosmologically viable EU scenario in the framework of massivegravity. Our analysis leads to certain constraints on the model parameters for the feasibility ofsuch a scenario.

Collaboration

B. C. Paul and A. S. Majumdar

Primary author: PAUL, Dr. Bikash Chandra (University of North Bengal)

Presenter: PAUL, Dr. Bikash Chandra (University of North Bengal)



28th Texas Symp … / Report of Contributions Marder’s Two-Fluid Dark Energy …


Marder’s Two-Fluid Dark Energy CosmologicalModels In Saez-Ballester Theory of Gravitation

AbstractThe present paper deals with cylindrically symmetric metric inthe form of Marder (1958) with Saez-Ballester theory of gravitationin the presence of perfectfluid and dark energy. In order to obtainthe deterministic solution of the field equations we have assumed thatthe expansion scalar in the model is proportional to the Eigen valueof the shear tensor. We have also assumed that the two sources, herethe perfectfluid and dark energy interact minimally with separateconservative parts of their energy momentum tensors together withthe constant EoS parameter of the perfectfluid. The role of the darkenergy in the present model with variable equation of state parameteris stuied more in detail. Some physical properties of model are alsodiscussed.

Primary author: Dr PAWAR, Dnyaneshwar (School of Mathematical Science,Swami RamanandTeerth Marathwada University, Nanded, 431606 (India))

Co-author: Mr SOLANKE, Yadao (Department of Mathematics, Mungasaji Maharaj Mahavidyalaya,Darwha,Dist. Yeotmal 445202)

Presenter: Dr PAWAR, Dnyaneshwar (School of Mathematical Science,Swami Ramanand TeerthMarathwada University, Nanded, 431606 (India))


28th Texas Symp … / Report of Contributions Born-Infeldizing gravity


Born-Infeldizing gravityMonday, December 14, 2015 3:24 PM (21 minutes)

In order to regularize the energy of point-like charged particles, Born and Infeld introduced amodification of the Maxwell lagrangian that naturally imposes an upper bound on electromagneticfields. This approach was later taken by Deser and Gibbons to propose an analogous modificationfor gravity. I will review these ideas and discuss a scenario where inflation could be supported bya set of massive particles within the context of these theories.

Primary author: HEISENBERG, Lavinia (ETHZ - ETH Zurich)

Presenter: HEISENBERG, Lavinia (ETHZ - ETH Zurich)



28th Texas Symp … / Report of Contributions Project QVADIS: Testing the exist …


Project QVADIS: Testing the existence of thegravitational anomalies by the study of

trans-Neptunian binariesThursday, December 17, 2015 6:25 PM (10 minutes)

The unrivalled advantage of tiny trans-Neptunian binaries is that they are the best available realisa-tion of an isolated two body system with very weak external and internal Newtonian gravitationalfield. As a consequence, in many cases (as for instance in the case of the binary (55637) 2002 UX25),the known Newtonian precession of orbit of the satellite is so small that cannot be detected by theexisting telescopes; hence an astronomer must observe the zero Newtonian perihelion precession.Fortunately, an observable precession of the orbit can be caused by an anomalous gravitationalfield as weak as 10-11m/s2 (with the next generation of telescopes the anomalous gravitationalfield of the order of 10-12m/s might be revealed). In brief, the measurement of a non-zero pre-cession would be sign of new physics, while the measurement of zero-precession would imposestrong limits on the size of the eventual gravitational anomalies. The goal of the emerging projectQVADIS is to measure the perihelion precession of tiny satellites in some trans-Neptunian binaries.While these measurements are significant independent of any theory they were initially proposedas a crucial test of a new model of the Universe based on the hypothesis that quantum vacuumfluctuations are virtual gravitational dipoles. According to the new model, the only content ofthe Universe is the known Standard Model matter (i.e. matter made from quarks and leptons in-teracting through the exchange of gauge bosons) immersed in the quantum vacuum “enriched”with virtual gravitational dipoles. Apparently, what we call dark matter and dark energy, can beexplained as the local and global effects of the gravitational polarization of the quantum vacuumby the immersed baryonic matter


Co-authors: VECCHIATO, Alberto (INAF, Torino, Italy); GAI, Mario (INAF, Torino, Italy); MITRO-VIC, Sandra (Institute of Physics, Astrophysics and Cosmology (ME))




28th Texas Symp … / Report of Contributions Hawking radiation cannot exist if …


Hawking radiation cannot exist if quantum vacuumfluctuations are gravitational dipoles


While it is neglected, Hawking radiation is model-dependent; it depends on our model of thequantum vacuum. It was recently suggested that what we call dark matter and dark energy can beexplained as the local and global effects of the gravitational polarization of the quantum vacuumby the immersed Standard Model matter. This result appears as the consequence of the working hy-pothesis that by their nature quantum vacuum fluctuations are virtual gravitational dipoles. Here,as a consequence of the same hypothesis we argue that instead of the nonexistent thermal Hawk-ing radiation there is a much stronger non-thermal radiation which is caused by the conversion ofvirtual particle-antiparticle pairs into real ones; this conversion happens deep inside the horizon.Contrary to Hawking radiation which leads to the black hole information paradox, there is noinformation loss paradox within the framework of the quantum vacuum “enriched” with virtualgravitational dipoles.





28th Texas Symp … / Report of Contributions Using Gamma-Ray Bursts as Cosm …


Using Gamma-Ray Bursts as Cosmological ProbesMonday, December 14, 2015 4:15 PM (20 minutes)

Although they are not standard candles, gamma-ray bursts (GRBs) are quite definitely cosmolog-ical objects, with some of the highest redshifts observed. The problem remains how to use GRBobservables to construct a usable Hubble diagram. Several correlations between observables andthe energetics have been noted, e.g. Amati et al. (2002) and Yonetoku et al. (2004), but it is notclear whether these suffer selection effects. I will discuss recent progress toward understandingthe origin of these correlations that opens a road towards the GRB Hubble diagram.

Primary author: PREECE, Rob (University of Alabama in Huntsville)

Presenter: PREECE, Rob (University of Alabama in Huntsville)



28th Texas Symp … / Report of Contributions A Cyclic Universe alternatively do …


A Cyclic Universe alternatively dominated by matterand antimatter


It was recently suggested that what we call dark matter and dark energy, can be explained as thelocal and global effects of the gravitational polarization of the quantum vacuum by the immersedStandard Model matter. This result appears as the consequence of the working hypothesis thatby their nature quantum vacuum fluctuations are virtual gravitational dipoles. Here, we arguethat, as a consequence of the same hypothesis, we may live in a cyclic universe with cycles al-ternatively dominated by matter and antimatter. At least mathematically there is no the initialsingularity, there is no need for the cosmic inflation and there is an amusing explanation of thematter-antimatter asymmetry in the universe: our universe is dominated by matter because theprevious cycle was dominated by antimatter (and the next cycle would be dominated by antimatteragain).

Primary author: HAJDUKOVIC, Dragan (Institute of Physics, Astrophysics and Cosmology)

Presenter: HAJDUKOVIC, Dragan (Institute of Physics, Astrophysics and Cosmology)



28th Texas Symp … / Report of Contributions The gravitational polarization of t …


The gravitational polarization of the quantumvacuum as a possible solution to the dark energy

problemMonday, December 14, 2015 6:08 PM (3 minutes)

Our study is based on the working hypothesis that by their nature quantum vacuum fluctuationsare virtual gravitational dipoles. This hypothesis is the simplest solution to the cosmological con-stant problem and opens the possibility to consider the known Standard Model matter (i.e. mattermade from quarks and leptons interacting through the exchange of gauge bosons) as the only con-tent of the Universe. If this hypothesis is correct, each galactic halo of hypothetical dark mattermust be replaced by the halo of the quantum vacuum polarized by the immersed baryonic mat-ter. Totality of all these halos is a cosmological fluid which during expansion of the Universeconverts from a fluid with negative pressure (allowing an accelerated expansion of the Universe)to a fluid with zero pressure (physically it means the end of the accelerated expansion). This forthe first time suggests, at least mathematically, quantum vacuum may explain both phenomena;phenomena usually attributed to dark matter and phenomena usually attributed to dark energy.





28th Texas Symp … / Report of Contributions Towards a unified model for the …


Towards a unified model for the gamma-ray burstprompt emission & a new luminosity-hardness

relation for cosmologyThursday, December 17, 2015 12:10 PM (20 minutes)

The Gamma Ray Bursts (GRBs) are the most intense explosions in the universe and the footprintsof stellar-mass black hole formation. Their initial phase, called prompt emission, lasts from afew ms to several tens of s. We suggest here to replace the historical spectral model (Band func-tion) for the GRB prompt emission (keV-MeV energy regime) with a new one. We show that thecomplex GRB spectro-temporal shapes are well described with a combination of three separatecomponents: (i) a thermal-like component that we interpret as emission from a non-dissipativeGRB jet photosphere, (ii) a non-thermal component that we interpret either as synchrotron radi-ation from charged particles propagating and accelerated within the GRB jet or as a dissipativephotosphere, and (iii) a second non-thermal component that is not always present or detectableand which is most likely of inverse Compton origin. The smooth evolution of all three compo-nents during the burst duration reinforces the validity of this new model. Detailed studies of theevolution of these components provide insights on the nature and composition of GRB jets as wellas on their magnetic fields. Moreover, this new model enables a new luminosity-hardness rela-tion based on the first non-thermal component showing that GRBs may be standard candles. Ifstatistically confirmed, this relation will be used to (i) constrain the mechanisms powering GRBjets, (ii) estimate GRB distances, (iii) probe the early Universe, and (iv) constrain the cosmologicalparameters in complement to the Type Ia SNe sample. I will present this new model using analysisof GRBs detected with various observatories and instruments such as Fermi, CGRO/BATSE andmore recently Swift. I will discuss here the striking similarities of GRB spectral shapes as well asthe possible universality of the proposed luminosity-hardness relation in the context of the newmodel.

Primary author: GUIRIEC, Sylvain (NASA Goddard Space Flight Center / UMD / CRESST)

Presenter: GUIRIEC, Sylvain (NASA Goddard Space Flight Center / UMD / CRESST)



28th Texas Symp … / Report of Contributions Parametric resonance after hilltop …


Parametric resonance after hilltop inflation causedby an inhomogeneous inflaton field


I will first give a short overview of preheating after hilltop inflation. In the main part of the talk Iwill discuss how the dynamics can changewhen the inflaton couples to another scalar field, e.g. a right-handed sneutrino, which provides amechanism for generating the correct initial conditions for inflation and also a decay channel forthe inflaton that allows for non-thermal leptogenesis. I will particularly discuss how the knownphases of preheating during which the inflaton field becomes fully inhomogeneous, can be fol-lowed by a subsequent preheating phase where the fluctuations of the secondary field gets res-onantly enhanced, from initially tiny amplitudes up to amplitudes of the same order (and evenlarger) as the ones of the inflaton field. This resonant enhancement differs from the usual para-metric resonance as the inflaton field is highly inhomogenous at the time the enhancement takesplace.

Primary authors: Mr NOLDE, David (University of Basel); CEFALÀ, Francesco (University ofBasel); ANTUSCH, Stefan (University of Basel); ORANI, Stefano (Basel University)

Presenter: CEFALÀ, Francesco (University of Basel)



28th Texas Symp … / Report of Contributions CMB spectral distortions


CMB spectral distortionsMonday, December 14, 2015 11:55 AM (35 minutes)

Presenter: Prof. SUNYAEV, Rashid



28th Texas Symp … / Report of Contributions The future for strong gravitational …


The future for strong gravitational lensingThursday, December 17, 2015 2:21 PM (21 minutes)

The Euclid mission is expected to discover perhaps two orders of magnitudemore strong gravitational lenses than are known today. These will be quasar-galaxy,galaxy-galaxy and galaxy-cluster lenses. I will discuss what is required to find andprocess such a large number of lenses. I will then describe what can be learned fromthese lenses with respect to the dark matter distribution, cosmology and gravitational theory. Inthe process I will discuss new methods for analysing lensing data.

Primary author: METCALF, R. Benton (Univerity of Bologna)

Presenter: METCALF, R. Benton (Univerity of Bologna)



28th Texas Symp … / Report of Contributions Observed properties of high redsh …


Observed properties of high redshift Gamma-RayBursts


I shall compare the observed properties of high redshift long Gamma-Ray Bursts with those atlower redshifts

Primary author: PIZZICHINI, Graziella (INAF)

Presenter: PIZZICHINI, Graziella (INAF)



28th Texas Symp … / Report of Contributions Varying constants entropic cosmo …


Varying constants entropic cosmologyTuesday, December 15, 2015 6:16 PM (3 minutes)

We formulate the basic framework of thermodynamical entropic force cosmology which allowsvariation of the gravitational constant G and the speed of light c. Three different approaches totheformulation of the field equations are presented. Some cosmological solutions for each frameworkare given and one of them is tested against combined observational data (supernovae, BAO, andCMB). From the fit of the data it is found that the Hawking temperature numerical coefficient γ istwo to four orders of magnitude less than usually assumed on the geometrical ground value ofO(1)and that it is also compatible with zero. Besides, in the entropic scenario we observationally testthat the fit of the data is allowed for the speed of light c growing and the gravitational constantG diminishing during the evolution of the universe. We also obtain a bound on the variation of cto be ∆c/c ∝ 10^−5 > 0 which is at least one order of magnitude weaker than the quasar spectraobservational bound.

Primary author: GOHAR, Hussain (University of Szczecin, Poland)

Presenter: GOHAR, Hussain (University of Szczecin, Poland)



28th Texas Symp … / Report of Contributions A new intrinsic intrinsic 3 parame …


A new intrinsic intrinsic 3 parameter correlation inGamma Ray Bursts


An analysis of 176 GRBs with known redshift observed by Swift which present afterglow plateaurevealed a new tri-parameter correlation (Lpeak,Lx,Ta) where Lpeak is the peak luminosity in theprompt emission, Lx is the luminosity at the end of the plateau emission and Ta is the rest frametime at the end of the plateau emission. We have already proven the intrinsic nature of the Lx-Ta (Dainotti et al. 2013a) and the Lpeak-Lx correlation (Dainotti et al. 2015b) through the Efron &Petrosian (1992) method.We here show the intrinsic slope of this new correlation whose intrinsic scatter is 10% less than the onefor the Lx-Ta correlation, therefore this new relation can be more useful as a cosmological tool.In addition, we show how the separation between categories of GRB-SNe, X-ray Flashes and shortGRBs with extended emission are displayed in the 3D space. It is advisable to divide the categoriesbefore using this correlation for cosmological study.Finally, we also present the Lpeak-T90 correlation, where T90 is the time where the 90% of the promptemission is emitted between 5% and 95%. This correlation is weaker than the Lpeak-Ta one, thusfavoring the choice of T*a as a preferred time as a third parameter in the 3D mentioned correlation.

Collaboration

Dainotti, Maria, Vahe’ Petrosian, sergey Postnikov, Shigehiro Nagataki, Capozziello Salvatore

Primary author: DAINOTTI, Maria (Stanford University)

Co-authors: OSTROWSKI, Michal (Jagiellonian University); Prof. CAPOZZIELLO, Salvatore (Uni-versity of Naples); Dr POSTNIKOV, Sergey (Bloomington University); NAGATAKI, Shigehiro (YukawaInstitute for Theoretical Physics, Kyoto University); PETROSIAN, Vahe’ (Stanford University)

Presenter: DAINOTTI, Maria (Stanford University)



28th Texas Symp … / Report of Contributions Heading into the abyss: X-ray spe …


Heading into the abyss: X-ray spectral timing ofaccreting black holes


The innermost region of the accretion flow around X-ray bright, unobscured, Active Galactic andBlack Hole Binaries (AGN and BHB) is being routinely mapped by X-ray spectral-timing of thereflection spectrum produced by irradiation of the accretion disc. The spin of the black hole can bedetermined by identifying the inner edge of the reflection region with the ISCO. The black hole inmany of the objects studied then appears to be rapidly spinning. When an object has high spin andthe corona lies close to the disc, as occurs some of the time for some sources, then most reflectionoriginates within one gravitational radius of the event horizon.

Primary author: Prof. FABIAN, Andrew (University of Cambridge)

Presenter: Prof. FABIAN, Andrew (University of Cambridge)



28th Texas Symp … / Report of Contributions A unifying description of dark ene …


A unifying description of dark energyTuesday, December 15, 2015 9:00 AM (35 minutes)

I will present an effective description of dark energy/modified gravity models involving a singlescalar field. It is based on a 3+1 splitting of space-time with respect to uniform scalar field hyper-surfaces. The advantage of this approach is that it can describe in the same language a vast numberof existing models, including quintessence, F(R) gravity, Horndeski theories, as well as recently in-troduced scalar-tensor theories “beyond” Horndeski. This approach provides a unified treatmentof linear cosmological perturbations, generically characterized by only five time-dependent func-tions. This gives an economic and systematic way to confront theoretical models with cosmologicalobservations.

Primary author: LANGLOIS, David (CNRS)

Presenter: LANGLOIS, David (CNRS)



28th Texas Symp … / Report of Contributions Two new relativistic MSPs from th …


Two new relativistic MSPs from the HTRU-NorthWednesday, December 16, 2015 2:55 PM (20 minutes)

We report on the two new MSP discoveries from the High Time Resolution Universe survey forpulsars and fast transients in the northern hemisphere (HTRU-North), being conducted with the100-m Effelsberg telescope (Barr et al, 2013). The survey has so far resulted in the total number of17 new pulsars. Here we present timing solutions for PSR J2045+3633 and PSR J2053+4650, bothbinary systems with massive companions (>0.8 M). Our objective is a precise mass measurementof the components of these binary systems.PSR J2045+3633 has a spin period of 31.68 ms, orbital period of 32.3 days and orbital eccentricitye = 0.017. Such eccentricity, high for pulsar-white dwarf systems and low for double neutronstar systems, indicates that this pulsar probably accreted very little matter from the massive, short-lived progenitor of its companion whose nature is not totally clear yet. Systems with eccentricitiesin this range are rare so are important for understanding the mildly-recycled pulsar population.Measuring their masses, we improve the sample of NS masses “at birth”. After one year of timingwith the Effelsberg, Jodrell Bank, Arecibo and Nançay telescopes the derived pulsar mass estimateis 1.64±0.27 M. The precision continues to improve quickly.PSR J2053+4650 has a spin period of 12.58 ms and a highly-inclined (84.5°) circular 2.45-day orbitwith a white dwarf companion. This high orbital inclination contributed to the detection of theShapiro delay in the first timing campaign with the Effelsberg telescope, which, in turn, combinedwith the Jodrell Bank and Nançay observations, allowed us to measure the pulsar mass up to 16%precision: 1.52±0.25 M .Both pulsars are very bright (timing residuals of order 2 μs for 30-minute observations are obtainedwith Effelsberg) and promise to be a valuable addition to the pulsar timing arrays.

Collaboration

HTRU-NORTH

Primary author: BEREZINA, Marina (Max Planck Institute for Radio Astronomy)

Co-authors: LYNE, Andrew (Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy,The University of Manchester); STAPPERS, Benjamin (Jodrell Bank Centre for Astrophysics, School ofPhysics and Astronomy, The University of Manchester); CHAMPION, David (Max Planck Institute forRadio Astronomy); COGNARD, Ismael (Laboratoire de Physique et Chimie de l’Environnement et del’ Espace – Université d’Orléans); SPITLER, Laura (Max Planck Institute for Radio Astronomy); GUILLE-MOT, Lucas (Laboratoire de Physique et Chimie de l’Environnement et de l’ Espace – Université d’Orléans); KRAMER,Michael (max Planck Institute for Radio Astronomy); FREIRE, Paulo (Max Planck Institute for RadioAstronomy); EATOUGH, Ralph (Max Planck Institute for Radio Astronomy)

Presenter: BEREZINA, Marina (Max Planck Institute for Radio Astronomy)



28th Texas Symp … / Report of Contributions Decoherence of cosmological mass …


Decoherence of cosmological massive neutrinosTuesday, December 15, 2015 6:40 PM (3 minutes)

The transition of cosmological massive neutrinos into the non-relativistic regime acts as a deco-herence process which also changes the oscillation probability, reaching different values for theasymptotic flavour composition. Furthermore, this effect could also increase the entropy insidethe neutrino ensemble, triggering the formation of bulk viscosity and introducing fluctuations inthe gravitational potential, which in turn induces secondary anisotropies in the cosmic microwavebackground by the integrated Sachs-Wolfe effect.

Primary author: BORIERO, Daniel

Co-authors: Prof. SCHWARZ, Dominik (Bielefeld University); Dr VELTEN, Hermano (UniversidadeFederal do Espirito Santo (UFES)

Presenter: BORIERO, Daniel



28th Texas Symp … / Report of Contributions Warm dark matter cosmological st …


Warm dark matter cosmological structures - fromcollapse to caustics and cores


Using cosmological simulations we explore the effects of warm dark matter (WDM) particles (e.g.sterile neutrinos)on the structure formation for different mass particles. Properties like the velocitydispersion and the damping of the fluctuation spectrum imprint a distinct signature on the struc-ture formation mechanism as well as on the evolution of structures and on the internal structureof halos. Although the properties of the warm dark matter particles are strongly model dependent,we find that the structure formation mechanism is qualitatively more complex than originally as-sumed, a hybrid between top-down collapse and bottom-up growth. Comparing warm dark mattersimulations with cold dark matter ones, we see that the internal structure of halos is also qualita-tively different in these two cases. These effects and the differences between warm and cold darkmatter can be tested with observations on both large scales and small scales.Finally we address some technical aspects in simulating warm dark matter.

Primary author: PADUROIU, Sinziana (University of Geneva)

Presenter: PADUROIU, Sinziana (University of Geneva)



28th Texas Symp … / Report of Contributions The high energy variability of V40 …


The high energy variability of V404 Cygni during theJune 2015 outburst


The black hole binary V404 Cygni exhibited an unprecedently bright outburst on 2015, June 15.Since then, many space and ground observing facilities monitored the flux from the source dur-ing several weeks, until its decline to a near-quiescent state in late July-August. The source wasextremely variable at all wavelenghts. The radio versus X-ray flux variations are reminiscent ofthe already observed correlation in this and other black hole sources, in which the luminosity isdominated by jet emission.The high energy instruments on board INTEGRAL detected an extremely variable emission dur-ing both bright and low luminosity phases, with dramatic variations of the hardness ratio on timescales of ~seconds. The analysis of the IBIS and SPI data reveals the presence of hard spectrain the brightest phases, compatible with thermal Comptonization with plasma temperature ~40keV. On the other hand, the soft (<10 keV) X-ray spectra observed by Swift, Chandra and NuS-TAR show large absorption column variations and indication for strong disk outflows. Given thestrong hardness variations detected in the range ~20-200 keV, we conclude that the overall variabil-ity originates from two distinct components, the first due to absorption and the other originatingvery close to the central accreting source, most probably related to relativistic ejection events.

Primary author: NATALUCCI, Lorenzo (Istituto di Astrofisica e Planetologia Spaziali, INAF)

Co-authors: Dr BAZZANO, Angela (Istituto di Astrofisica e Planetologia Spaziali, INAF); JOUR-DAIN, Elisabeth (Universite de Toulouse; UPS-OMP; CNRS; IRAP); Dr ROQUES, Jean-Pierre (Univer-site de Toulouse; UPS-OMP; CNRS; IRAP); FIOCCHI, Mariateresa (Istituto di Astrofisica e PlanetologiaSpaziali, INAF); UBERTINI, Pietro (Istituto di Astrofisica e Planetologia Spaziali, INAF)

Presenter: NATALUCCI, Lorenzo (Istituto di Astrofisica e Planetologia Spaziali, INAF)

28th Texas Symp … / Report of Contributions UV sensitivity of Higgs inflation


UV sensitivity of Higgs inflationMonday, December 14, 2015 5:35 PM (20 minutes)

The idea of introducing a non minimal coupling between the Higgs boson and the gravity sectorgives successful predictions for inflation without needing new particles beyond the ones we know.Quantum mechanically the model is only consistent until the unitarity cutoff.Possible UV completions beyond this cutoff could change its predictions. If this is the case it meansthat we would lose the minimalist approach that inspires the model.Treating Higgs inflation in the context of effective field theories we consider the effect of thresholdcorrections on the renormalization group flow. We show that the CMB predictions are protectedfrom this type of UV corrections.

Primary author: Mr FUMAGALLI, Jacopo (Nikhef)

Co-author: Dr POSTMA, Marieke (Nikhef)

Presenter: Mr FUMAGALLI, Jacopo (Nikhef)



28th Texas Symp … / Report of Contributions Recent results from the ANTARES …


Recent results from the ANTARES deep-sea neutrinotelescope


The ANTARES experiment has been running in its final configuration since 2008. It is the largestneutrino telescope in the Northern hemisphere. After the discovery of a cosmic neutrino diffusefluxby the IceCube detector, the search for its origin has become a key mission in high-energyastrophysics. Particularly interesting is the indication (although not significant with the presentIceCube statistics) of an excess of signal events from the Southern sky region.

The ANTARES sensitivity is large enough to constrain the origin of the IceCube excess from re-gionsextended up to 0.2 sr in the Southern sky. Assuming different spectral indexes for the energyspectrum of neutrino emitters, the Southern sky and in particular central regions of our Galaxyarestudied searching for point-like objects and for extended regions of emission.The search program also includes multi-messenger analyses requiring time and/or space coinci-dences with other cosmic probes (cosmic rays, gamma rays or gravitational waves).

ANTARES has also provided results on atmospheric neutrinos and searches for rare particles (suchasmagnetic monopoles and nuclearites in the cosmic radiation). Of particular note are thesearches for Dark Matter: the limits obtained for the spin-dependent WIMP-nucleon cross sectionovercome that of existing direct-detection experiments.

Collaboration

ANTARES Collaboration

Primary author: Dr VIVOLO, Daniele (INFN Napoli)

Co-author: Dr PRADIER, Thierry (IPHC & University of Strasbourg)

Presenter: Dr VIVOLO, Daniele (INFN Napoli)



28th Texas Symp … / Report of Contributions Texas 2017 - Cape Town


Texas 2017 - Cape TownFriday, December 18, 2015 3:35 PM (10 minutes)

Presenter: Prof. BOETTCHER, Markus (North-West University)


28th Texas Symp … / Report of Contributions Einstein’s legacy: 100 years of gen …


Einstein’s legacy: 100 years of general relativityTuesday, December 15, 2015 7:30 PM (1h 30m)

Einstein’s theory of general relativity revolutionised our understanding of the cosmos, its originand its fate. Not surprisingly, it is one of the best tested theories, and so far all of its predictions havebeen confirmed. Einstein himself did not know many of the tests we can do today, 100 years aftergeneral relativity was presented by him. The most modern tests involve ultra-compact neutronstars, black holes, or ripples in space-time called gravitational waves. Perhaps surprisingly, generalrelativity, and the research into it, can also be encountered in daily life - perhaps well hidden, butpresent nevertheless. This talk will present some of the most exciting tests of general relativity,the fascinating objects that we use to study it, and reveal some of the connections to daily life.

Primary author: Prof. KRAMER, Michael (Max-Planck-Institut fuer Radioastronomie)

Presenter: Prof. KRAMER, Michael (Max-Planck-Institut fuer Radioastronomie)

Session Classification: Public talk


28th Texas Symp … / Report of Contributions Discussion session on averaging a …


Discussion session on averaging and backreaction incosmology




28th Texas Symp … / Report of Contributions Study of the galactic cosmic ray en …


Study of the galactic cosmic ray energy spectrumwith the ARGO-YBJ experiment


The CR spectrum has been studied by the ARGO-YBJ experiment in a wide energy range (TeVs→PeVs) . This study is particularly interesting because not only it allows a better understanding of theso called ’knee’ of the energy spectrum and of its origin, but also provides a powerful cross-checkamong very different experimental techniques.

The unique detector features (full coverage, time resolution, large dynamic range) and location(4300 m above sea level) allowed both lowering the energy threshold down to the region coveredby direct measurements and reaching the knee of the all-particle spectrum, where data from manyground-based experiments are available since long time. Moreover, the possibility of a detailedstudy of the particle distribution at ground in the first few meters from the shower axis, provided anew and efficient way of selecting events initiated from light mass primaries (i.e. protons and alphaparticles), without relying on the muon signal, thus avoiding sizeable systematic dependencies onthe adopted hadronic interaction model.

The resulting all-particle spectrum (measured in the energy range 100 TeV - 10 PeV) is in goodagreement with both theoretical parametrizations and previous measurements, thus validatingthe selection and reconstruction procedures.

The light-component (i.e. p + He) has been measured from 3 TeV up to about 3 PeV. The ARGO-YBJresult, while being in agreement with highest energy direct measurements, shows a clear indica-tion of a bending below 1 PeV. This provides new important inputs to acceleration/propagationmodels for galactic cosmic rays.

Collaboration

ARGO-YBJ

Primary authors: SURDO, Antonio (INFN - Lecce (IT)); DE MITRI, Ivan (Universita del Salento(IT))

Presenter: SURDO, Antonio (INFN - Lecce (IT))



28th Texas Symp … / Report of Contributions Pulsar timing detection of gravitat …


Pulsar timing detection of gravitational waves fromsupermassive black hole binaries in stellar

environmentThursday, December 17, 2015 6:25 PM (20 minutes)

We study the effect of stellar environment on gravitational wave spectrum produced by supermas-sive black hole binaries (SBHB). Our model includes the possibility of rotating galactic nucleus,which opens a new degree of freedom - the orientation of SBHB’s orbital plane - and significantlyaffects its eccentricity evolution. The result of our work is a model spectrum of stochastic gravita-tional wave background which can be tested by pulsar timing array observations.

Primary author: RASSKAZOV, Alexander

Co-author: MERRITT, David (Rochester Institute of Technology)

Presenter: RASSKAZOV, Alexander


Track Classification: Pulsar timing arrays (6 talks)


28th Texas Symp … / Report of Contributions Refinements of Jungle Universes


Refinements of Jungle UniversesMonday, December 14, 2015 6:15 PM (3 minutes)

How effective barotropic matter can emerge from the interaction of cosmological fluids in anisotropic and homogeneous cosmological model ?

The dynamics of homogeneous and isotropic Friedmann-Lemaître-Robertson-Walker universes isa natural special case of generalized Lotka-Volterra systems where each of the universe’s fluidcomponents can be seen as a competitive species in a predator-prey model. (Jungle universearXiv:1306.1037v2)

In addition to numerical simulations illustrating this behaviour among the barotropic fluids fillingthe universe, we analytically pinpoint that effective time-dependent barotropic indices can arisefrom a physical coupling between those fluids which dynamics could then look like that of anothertype of cosmic fluid, such as a cosmological constant.

As the nature of dark energy still remains discussed today, this dynamical approach could helpunderstanding some of the properties of dark matter and dark energy at large cosmological scales.

Primary authors: SIMON-PETIT, Alicia (Applied Mathematics Laboratory, ENSTA ParisTech,Université Paris-Saclay); YAP, Han Hoe (Applied Mathematics Laboratory, ENSTA ParisTech, Uni-versité Paris-Saclay); PEREZ, Jérôme (Applied Mathematics Laboratory, ENSTA ParisTech, UniversitéParis-Saclay)

Presenter: SIMON-PETIT, Alicia (Applied Mathematics Laboratory, ENSTA ParisTech, UniversitéParis-Saclay)



28th Texas Symp … / Report of Contributions Welcome address by the Vice- …


Welcome address by the Vice-Rector of theUniversity of Geneva


Presenter: Prof. TRISCONE, Jean-Marc (University of Geneva)

Session Classification: Cover


28th Texas Symp … / Report of Contributions Introduction


IntroductionMonday, December 14, 2015 9:00 AM (7 minutes)



28th Texas Symp … / Report of Contributions Einstein’s Swiss Years


Einstein’s Swiss YearsMonday, December 14, 2015 9:15 AM (20 minutes)

Presenter: Prof. LACKI, Jan (University of Geneva)



28th Texas Symp … / Report of Contributions Joint constraints on neutrino mass …


Joint constraints on neutrino mass and number ofeffective neutrino species from cosmology


We present joint constraints on the number of effective neutrino species Neff and the sum of neu-trino masses, using a technique based on state-of-the-art hydrodynamical simulations with mas-sive neutrinos, which allows one to exploit the full information contained in the one-dimensionalLyman-Alpha forest flux power spectrum complemented by additional cosmological probes. Ourresults provide strong evidence for the cosmic neutrino background (Neff = 0 is rejected at morethan 14σ), and rule out the possibility of a sterile neutrino thermalized with active neutrinos at asignificance of over 5σ – one of the strongest bounds to date.

Primary author: ROSSI, Graziano (Sejong University)

Co-authors: YECHE, Christophe (CEA-Saclay); LESGOURGUES, Julien; PALANQUE-DELABROUILLE,Nathalie (CEA)

Presenter: ROSSI, Graziano (Sejong University)



28th Texas Symp … / Report of Contributions Texas 2015 & Nepal


Texas 2015 & NepalFriday, December 18, 2015 3:30 PM (5 minutes)


28th Texas Symp … / Report of Contributions High-precision cosmology and inh …


High-precision cosmology and inhomogeneities:exact results in the geodesic light-cone gauge


The remarkable properties of the recently proposed geodesic light-cone (GLC) gauge allow to getsome new interesting results to face the problem of inhomogeneities and their backreaction. In-deed, GLC simply consists of gauge fixing the metric tensor on the past light-cone of the observer.Thanks to this choice, several interesting physical observables, related to photons, can be evalu-ated within this framework. In this talk, we will present an overview on these recent results: inparticular, we will show how the geodesic deviation equation can be exactly solved, giving an ex-act expression for the so called Jacobi map. Furthermore, its link with cosmological distances andweak gravitational lensing will be discussed.

Primary author: FANIZZA, Giuseppe (Università degli Studi di Bari ”Aldo Moro”)

Presenter: FANIZZA, Giuseppe (Università degli Studi di Bari ”Aldo Moro”)



28th Texas Symp … / Report of Contributions Large Scale Density profiles surro …


Large Scale Density profiles surrounding extremas inthe density field as cosmological probes

In this work I show that we can reconstruct the large scale density profiles surrounding extremain the density field such as Dark Matter Halos or Cosmic Voids (their exact symmetric in the initialconditions).

I show that those profiles can be parametrized in such a way that they conserve some inner prop-erties in their evolution whatever the underlying dynamics. Using N-body simulations of ΛCDMcsomology, we show that this conserved quantity can be used to reconstruct the analytical profileat any redshift.

The observed stacked profiles, combined with the peculiar velocity profile, can then be used toconstrain directly cosmology and in particular Dark Energy and even the nature of Gravity itself.This approach will find its interest in the upcoming Large Scale Surveys which will probe suchcosmological scales with a sufficient statistics.

Primary author: DE FROMONT, Paul (Observatoire de Paris - LUTH)

Presenter: DE FROMONT, Paul (Observatoire de Paris - LUTH)


Report of Contributions - CERN Indico

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