1

Julia G. Barzyk

Department of the Geophysical Sciences University of Chicago

The Chicago Center for CosmochemistryMaterials Science Division, Argonne National Laboratory

Prepared for

Astronomy with Radioactivities VClemson University - Clemson, SC 29634

September 5-9, 2005

J.G. Barzyk 1,2,3; M.R. Savina 2,3; M.J. Pellin 2,3; A.M. Davis 1,3,4; R.S. Lewis 3,4; and R.N. Clayton 1,3,4,5.

(1) Department of the Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637(2) The Chicago Center for Cosmochemistry, 5734 South Ellis Avenue, Chicago, IL 60637(3) Materials Science Division, Argonne National Laboratory, Argonne, IL 60439(4) Enrico Fermi Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637(5) Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago. IL 60637

Multi-element isotopic analysis of single presolar SiC grains

2

Presolar SiC

•presolar grains identified in meteorites based on extreme isotopic deviations from solar(Lewis et al., (1987) Nature 326, 160-162)

•grains isolated from the Murchison meteorite (Amari et al. (1994) Geochim. Cosmochim. Acta 58, 459-470)•Mo, Zr, and Ba isotopic compositions measured by Resonant Ionization Mass

Spectrometry using Chicago-Argonne Resonant Ionization Spectrometer for MicroAnalysis (Savina et al. (2003) Geochim. Cosmochim. Acta 67, 3215-3225)

KJHJB-D2-12 before analysis KJHJB-D2-12 after analysis

3

CHARISMA

4

Classification of presolar grains

Mainstream grains are formed in envelopes of low mass AGB stars of ~solar metallicity

Zinner E. (1998) Annu. Rev. Earth Planet. Sci. 26, 147-188.

5

Multi-element isotopic analysis in single presolar SiC

• 93 grains attempted for ≥ 1 element• Data collected for ≥ 1 element on 55

grains, insufficient counts obtained for 38 grains

• 9/55 have non-s-process signatures• 7% of all presolar grains are non-

mainstream• 16% in this study are non-

mainstream• Possible that a higher fraction than

7% of large, heavy element-rich grains are non-mainstream

XMo

92 94 96 98 100

δ(X M

o/96

Mo)

-900

-800

-700

-600

-500

-400

-300

-200

-100

s-process

6

Mo: Chart of Nuclides

90Zr51.5

91Zr11.2

92Zr17.2

93Zr1.5My

94Zr17.4

95Zr64d

96Zr2.80

97Zr17h

93Nb100

94Nb20ky

95Nb35d

92Mo14.8

94Mo9.25

95Mo15.9

96Mo16.7

97Mo9.55

98Mo24.1

99Mo66h

100Mo9.63

99Tc210ky

100 Tc15s

96Ru5.52

98Ru1.88

99Ru12.7

100Ru12.6

101Ru17.0

102 Ru31.6

103 Ru39d

104 Ru18.7

N=5

0

95Nb23h

•solar abundance fairly evenly distributed among 7 stable isotopes•unusually high abundance of p-only isotope

7

Previous work on Mo in mainstream grains

Nicolussi et al. (1998) Geochim. Cosmochim Acta 62, 1093-1104Davis et al. (1999) LPS XXX

10001

MoMo

MoMo

) ‰(MoMo

standard96

Xsample

96

X

96

X

×

⎟⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜⎜

⎝

⎛

−

⎟⎟⎠

⎞⎜⎜⎝

⎛

⎟⎟⎠

⎞⎜⎜⎝

⎛

=⎟⎟⎠

⎞⎜⎜⎝

⎛δ

8

Previous work on Mo in mainstream grains

Lugaro et al. (2003) Astrophys. J. 593 (1), 486-508

9

Neutron sources in Asymptotic Giant Branch (AGB) starsGallino, et al. ApJ, 497, 388-403 (1998)

• 13C pocket: quasi-continous low-flux neutron source via 13C(α,n)16O

• Responsible for most n-capture nucleosynthesis in AGB stars

• He-burning: brief high-flux neutron source via 22Ne(α,n)25Mg

• Thermal pulses “homogenize” the shell structure via 3rd dredge-up

convective envelope

C/O

HeHH--burning shellburning shell

10

Previous work on Mo in mainstream grains

Lugaro et al. (2003) Astrophys. J. 593 (1), 486-508

11

δ(92Mo/96Mo)

-1000 -800 -600 -400 -200 0 200

δ(94

Mo/

96M

o)

-1000

-800

-600

-400

-200

0

200

SiC grainsd12d6 d3 d2 d1.5 st u1.3 u2

Mo data: single element plot

12

Zr: Chart of Nuclides

89Y100

90Y64h

91Y59d

92Y3.5h

90Zr51.5

91Zr11.2

92Zr17.2

93Zr1.5My

94Zr17.4

95Zr64d

96Zr2.80

97Zr17h

93Nb100

94Nb20ky

95Nb35d

92Mo14.8

94Mo9.25

95Mo15.9

96Mo16.7

97Mo9.55

98Mo24.1

99Mo66h

100Mo9.63

95Nb23h

6 stable isotopes of Zr with 96Zr affected largely by activation of 22Ne n-source

13

Mo and Zr 2-element plots: previous work

Lugaro et al. (2003) Astrophys. J. 593 (1), 486-508

14

Mo and Zr: 2-element plot (1)

δ(92Mo/96Mo)

-1000 -800 -600 -400 -200 0 200 400

δ(96

Zr/9

4 Zr)

-1000

-800

-600

-400

-200

0

200

400

SiC graind12, 1.5 Md6, 1.5 d3, 1.5 d2, 1.5 d1.5, 1.5 st, 1.5 u1.3, 1.5 u2, 1.5 d12, 3 d6, 3 d3, 3 d2, 3 d1.5, 3 st, 3 u1.3, 3 u2, 3

15

Mo and Zr: 2-element plot (2)

δ(92Mo/96Mo)

-1000 -800 -600 -400 -200 0 200 400

δ(96

Zr/9

4 Zr)

-1000

-800

-600

-400

-200

0

200

400

SiC graind12, 1.5 Md6, 1.5 d3, 1.5 d2, 1.5 d1.5, 1.5 st, 1.5 u1.3, 1.5 u2, 1.5 d12, 3 d6, 3 d3, 3 d2, 3 d1.5, 3 st, 3 u1.3, 3 u2, 3

16

Mo data with contaminated grains removed

δ(92Mo/96Mo)

-1000 -800 -600 -400 -200 0 200

δ(94

Mo/

96M

o)

-1000

-800

-600

-400

-200

0

200

SiC grainsd12d6 d3 d2 d1.5 st u1.3 u2

17

Ba: Chart of Nuclides

139La99.9

138La0.09

140La40h

128Xe1.91

129Xe26.4

130Xe4.1

131Xe21.2

132Xe26.9

133Xe5.3d

134Xe10.4

136Xe8.9

133Cs100

134Cs2.1y

135Cs2.0My

136Cs13d

137Cs30y

138Cs32m

130Ba0.11

132Ba0.10

134Ba2.42

135Ba6.59

136Ba7.85

137Ba11.2

138Ba71.7

139Ba83m

139La99.9

138La0.09

140La40h

N=8

2

5 stable isotopes abundant enough to be measured in individual grainsBranch points at 134Cs and 136Cs control Ba isotopic composition

18

Ba: previous work

-1000 -800 -600 -400 -200 0 200-600

-400

-200

0

200

400

600 137Ba SiC grains 1.5 M model 3 M model 5 M model

δ135Ba/136Ba (‰)

δ137 Ba

/136 Ba

(‰)

Savina et al. (2003) Geochim. Cosmochim. Acta 67, 3201-3214

19

Ba and Zr: 2-element plots (1)

δ(135Ba/136Ba)

-1000 -800 -600 -400 -200 0 200 400

δ(96

Zr/9

4 Zr)

-1000

-800

-600

-400

-200

0

200

400

SiC graind12, 1.5 d6,1.5 d3, 1.5 d2, 1.5 d1.5, 1.5 st, 1.5 u1.3, 1.5 u2, 1.5 d12, 3 d6, 3 d3, 3 d2, 3 d1.5, 3 st, 3 u1.3, 3 u2, 3

20

Ba and Zr: 2-element plots (2)

δ(135Ba/136Ba)

-1000 -800 -600 -400 -200 0 200 400

δ(96

Zr/9

4 Zr)

-1000

-800

-600

-400

-200

0

200

400

SiC graind12, 1.5 d6,1.5 d3, 1.5 d2, 1.5 d1.5, 1.5 st, 1.5 u1.3, 1.5 u2, 1.5 d12, 3 d6, 3 d3, 3 d2, 3 d1.5, 3 st, 3 u1.3, 3 u2, 3

21

Ba data with contaminated grains removed

δ(135Ba/136Ba)

-1000 -800 -600 -400 -200 0 200

δ(13

7 Ba/

136 B

a)

-800

-600

-400

-200

0

200

SiC graind12, 1.5 d6, 1.5 d3, 1.5 d2, 1.5 d1.5, 1.5 st, 1.5 u1.3, 1.5 u2, 1.5 d12, 3 d6, 3 d3, 3 d2, 1.5 d1.5, 3 st Ba, 3 u1.3, 3 u2, 3

22

Non-s-process grains

9 grains out of 55 analyzed for at least one element appear to be non-s-process

XMo

92 94 96 98 100

δ(X M

o/96

Mo)

-1000

-500

0

500

1000

1500

2000

s-process A3-02 A3-05 B2-03 B2-05 B4-09 C3-08 F1-01

23

Discussion

• New Mo, Zr and Ba data indicate that model predictions using 13C pocket size close to “standard” case best explain observations

• Mo and Ba contamination could explain previous results

• Possible that non-mainstream grains are > 7% in large heavy element-rich grain fractions

• Will be important to obtain C, N, and Si data for non-s-process grains, s-process grains, and grains in which heavy elements were not detected