Pablo Torne

Application of TES bolometers and KID cameras to pulsar observations

Pablo Torne

RadioNet Workshop on Future Trends in Radio Astronomy Instrumentation (2020 Sep. 20/21)

East Asian Observatory — EAO (Hilo, Hawaii) Instituto de Radio Astronomía Milimétrica — IRAM (Granada, Spain)

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with J. Macías-Perez (LPSC-Grenoble), B. Ladjelate (IRAM), A. Ritacco (IAS-Orsay, LPENS-Paris), M. Sánchez-Portal (IRAM), S. Berta (IRAM), G. Paubert (IRAM), M. Calvo (I. Néel-Grenoble), G. Desvignes (MPIfR-Bonn, LESIA-Obs. Paris), R. Karuppusamy (MPIfR), S. Navarro (IRAM), D. John (IRAM), S. Sánchez (IRAM), J. Peñalver (IRAM), M. Kramer (MPIfR-Bonn, U. Manchester-UK), K. F. Schuster (IRAM), G. Bell (EAO-Hilo), D. Bintley (EAO-Hilo), and Paul Ho (EAO-Hilo)

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Application of TES bolometers and KID cameras to Pulsar Observations

Talk contents

Pablo Torne RadioNet Workshop in Future Trends in Radio Astronomy Instrumentation (2020 Sep. 20/21)

• Context • Caveats for (sub)mm- observations • Discussion of what do we need / have • Continuum cameras at focus • Results with the NIKA2 KID camera • Results with the SCUBA2 TES bolometer • Future, what else? • Summary & conclusions

ESO/L. Calçada

Adam et al. (2018)

Bintley et al. (2014)

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2. Obtaining Spectral Energy Distributions (SED), and emission properties of pulsars enable tests and refinement of pulsar magnetospheric and emission models

Input from observations

Adapted from Michel (1982)

1. The radio emission mechanism of pulsars is still a mystery

- Emission is coherent, i.e., amplified (but not pure relativistic synchrotron)

- Unknown amplification process

Open question

?

Credit: Lorimer & Kramer (2005)

see e.g., Melrose (2017)

3. Pulsars typically observed at centimetre wavelengths ~(0.1 - 10 GHz), and X-rayDetecting and studying them at other wavelengths difficult by lack of sensitivity, but valuable for emission research

Challenge

Here is where continuum cameras in the mm- to UV can help

↓


Context (I)

NIKA2 KID array; Credit: Institut Neel

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Context (II)Crab Pulsar

PSR B0531+21

Vela PulsarPSR B0833-45

Large gap between ~10 GHz and X-ray where only a handful of pulsars were detected

Smith (1977) Mignani et al. (2017)

NASANASA

see Wielebinski (2000), Mignani et al. (2019), [ApJ] and references therein

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• Pulsar signals are broadband (although not necessarily showing at all wavelengths) • They get dispersed (frequency-dependent velocity) in the interstellar medium (ISM) • At centimetre wavelengths one needs spectral resolution to correct this (= de-dispersion) • But dispersion effect is tiny (~negligible) at above tens of GHz = No need of frequency resolution !

A couple of caveats: Dispersion in the ISM

Example: DM = 500 cm-3 pc

𝛎 = 1 GHz, ∆𝛎 = 300 MHz; ∆t = 1.3 s

𝛎 = 100 GHz, ∆𝛎 = 8000 MHz; ∆t = 33 𝝻s

Number of free electrons on line of sight

see e.g., Lorimer & Kramer (2005)Condon & Ransom (2016)

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• Typically, we want to resolve the pulsations from the pulsars • Rule-of-thumb: minimum 32 samples per rotation, ideally many more (128 to 2048 bins) • Receiver+Backend need high time sampling capabilities• A few pulsars (magnetars) rotate slowly and are bright at (sub)mm- wavelengths

A couple of caveats: Time resolution

Example with Fs ≃ 23 Hzdetectable pulsars

Magnetars

Pulsar populationXTE J1810-197 detection @ 150 GHz

# profile points ↔ details ↔ detection + science

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• To be able to detect the weak pulsations at short wavelengths we need:- Enormous sensitivity- Fast time sampling capabilities

Minimum detectable flux density at S/N level

Big collecting areas

Good sites and state-of-the-art receivers

Large instantaneous bandwidthsLong integration times

[Jy]

Pulsar observations at (sub)mm- wavelengths

Radiometerequation:

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[Jy]


Usually 5-25x higher than cm-𝛌 (Tsky!)

~10-20x lower than cm-𝛌(dish size ~small)

• At (sub)millimeter telescopes we get:- Low sensitivity compared to cm- telescopes (smaller dishes, higher Tsys)- Usually, no fast time sampling capabilities

Radiometerequation:

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• At (sub)millimeter telescopes we get:- Low sensitivity compared to cm- telescopes (smaller dishes, higher Tsys)- Usually, no fast time sampling capabilities- Continuum cameras: very large bandwidths + high time sampling





[Jy]


Usually 5-25x higher than cm-𝛌 (Tsky!)

~10-20x lower than cm-𝛌(dish size ~small)

Radiometerequation:

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(Sub)mm- continuum cameras at focus

NIKA2 @ IRAM 30m Telescope SCUBA2 @ JCMT

• Theoretically feasible to apply them to observe pulsars • Available (with two different technologies) at two of the largest facilities

IRAM/DiVertiCimes James Clerk Maxwell Telscope

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NIKA2 @ IRAM 30m Telescope

• Kinetic Inductance Detector, 2896 KIDs @ T~150 mK • 2 mm (150 GHz) and 1.15 mm (260 GHz) • Field-of-View = 6.5 arcmin2 •Bandwidth ~35 GHz@2 mm, [email protected] mm•NEFD ~9±1 mJy·s1/2 @ 2 mm, ~30±3 mJy·s1/2 @ 1.15 mm•Standard sampling Fs = 23.84 Hz (max. Fs~500 Hz)• Linear polarisation in the 260 GHz band

more info: Adam et al. (2018), Perotto et al. (2020)

https://ipag.osug.fr/nika2//Instrument.html

Adam et al. (2018)

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• Transition Edge Sensors, 10240 TESs @ T~50 mK • 0.85 mm (352 GHz) and 0.45 mm (666 GHz) • Field-of-View = 43 arcmin2 •Bandwidth ~35 [email protected] mm // [email protected] mm•NEFD ~90 mJy·s1/2 @ 0.85 mm, ~400 mJy·s1/2 @ 0.45 mm•Standard sampling (average) Fs = 200 Hz• Linear polarisation and spectroscopy with ancillary instruments

more info: Holland et al. (2013), Chapin et al. (2013), Dempsey et al. (2013)

SCUBA2 @ JCMT

Bintley et al. (2014)

J. Dempsey talk

http://science-media.org/userfiles/40/presentations/40_presentation_108.pdf

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Tests + Results with NIKA2 @ IRAM 30m• Adapted observing mode: STARE on pulsar, continuous sampling• Data from a number of pixels around calculated source position • Reformatted data: ASCII -> Binary time series • Used standard pulsar analysis software (PRESTO) • Calibrated using standard methods for NIKA2 • … and worked beautifully

100 150 200 250 300Frequency (GHz)

5

10

15

20

Ave

rage

dF

lux

Den

sity

(mJy

)

↵ = �1.1 ± 0.3

1-� contour

NIKA2 data

10.5

12.0

13.5

A

�2.4

�1.8

�1.2

�0.6

↵

�2.4

�1.8

�1.2

�0.6

↵

Average pulse profiles of XTE J1810-197

Rotational phase Rotational phase

Spectral index fit

1.25 s

Torne et al. (2020), A&A 640, L2; https://ui.adsabs.harvard.edu/abs/2020A%26A...640L...2T/abstract

Zoom to magnetar XTE J1810-197 time series + single pulses (2 mm frequency band)

https://ui.adsabs.harvard.edu/abs/2020A%26A...640L...2T/abstract

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Tests + Results with SCUBA2 @ JCMT• Adapted observing mode: small custom Daisy, maximise good pixels and select sensitive arrays• Used tables to track the position of the pulsar while moving array • Used standard JCMT analysis tools (Starlink) • Calibrated using standard methods for SCUBA2 • … and worked beautifully, too!

Torne P., Bell G., et al., in prep.

Array comparison (top 850 um, bottom 450 um)

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Tests + Results with SCUBA2 @ JCMT• First detection of pulsations from a neutron star in the submillimetre band (𝛌 = 850 𝝻m = 0.85 mm)

• No detection at 450𝝻m (~10x less sensitivity)

t= 5.5 st= 0 s

FoV folded at pulsar period (Speed = 2x)




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Future, what else?• Sensitivity of the continuum cameras is ~at technological limit • Main improvable limitation is the maximum sampling frequency • Increase the sampling frequency would expand their application to pulsar observations • Apply same / similar technology at other telescopes (APEX?) • Potential use in infrared to optical wavelengths

Smith (1977)

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Summary and Conclusions

• Continuum cameras can be used to study pulsars in the (sub)mm- range

• High sensitivity counteracts a bit the drawback of small dishes and high Tsys

• May offer high time sampling capabilities by design

• Tested successfully with KIDs and TESs technology (NIKA2 and SCUBA2)

• Minimal adaptation needed, mainly only software

• Applies to a highly under-explored spectral region of pulsars

• Same or similar techniques at other telescopes & infrared / optical

Thank you !

Pablo Torne

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