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Title: Simultaneous iron and nickel isotopic analyses of presolar silicon carbide grains

Aside from recording stellar nucleosynthesis, a few elements in presolar grains can also provide insights into the galactic chemical evolution (GCE) of nuclides. We have studied the carbon, silicon, iron, and nickel isotopic compositions of presolar silicon carbide (SiC) grains from asymptotic giant branch (AGB) stars to better understand GCE. Since only the neutron-rich nuclides in these grains have been heavily in uenced by the parent star, the neutron-poor nuclides serve as GCE proxies. Using CHILI, a new resonance ionization mass spectrometry (RIMS) instrument, we measured 74 presolar SiC grains for all iron and nickel isotopes. With the CHARISMA instrument, 13 presolar SiC grains were analyzed for iron isotopes. All grains were also measured by NanoSIMS for their carbon and silicon isotopic compositions. A comparison of the measured neutron-rich isotopes with models for AGB star nucleosynthesis shows that our measurements are consistent with AGB star predictions for low-mass stars between half-solar and solar metallicity. Furthermore, our measurements give an indication on the 22Ne( ,n) 25Mg reaction rate. In terms of GCE, we nd that the GCE-dominated iron and nickel isotope ratios, 54Fe/56Fe and 60Ni/ 58Ni, correlate with their GCE-dominated counterpart in silicon, 29Si/ 28Si. The measured GCE trends include themore » Solar System composition, showing that the Solar System is not a special case. However, as seen in silicon and titanium, many presolar SiC grains are more evolved for iron and nickel than the Solar System. This con rms prior ndings and agrees with observations of large stellar samples that a simple age-metallicity relationship for GCE cannot explain the composition of the solar neighborhood.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [4]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of Chicago, IL (United States); Chicago Center for Cosmochemistry, Chicago, IL (United States)
  2. Univ. of Chicago, IL (United States); Chicago Center for Cosmochemistry, Chicago, IL (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Univ. of Chicago, IL (United States); Chicago Center for Cosmochemistry, Chicago, IL (United States); Univ. of Chicago, IL (United States). Enrico Fermi Inst.
  5. Univ. of Chicago, IL (United States); Chicago Center for Cosmochemistry, Chicago, IL (United States); Univ. of Chicago, IL (United States). Enrico Fermi Inst.; Argonne National Lab. (ANL), Argonne, IL (United States)
  6. Univ. of Chicago, IL (United States); Chicago Center for Cosmochemistry, Chicago, IL (United States)
  7. Washington Univ., St. Louis, MO (United States)
  8. Univ. of Torino (Italy)
  9. Univ. of Torino (Italy); Istituto Nazionale di Astrofisica (INAF), Torino (Italy)
  10. Osservatorio Astronomico di Teramo (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Perugia (Italy)
Publication Date:
Report Number(s):
LLNL-JRNL-723517
Journal ID: ISSN 0016-7037; TRN: US1800695
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 221; Journal Issue: C; Journal ID: ISSN 0016-7037
Publisher:
The Geochemical Society; The Meteoritical Society
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS
OSTI Identifier:
1414366