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Barium isotopes in individual presolar silicon carbide grains from the Murchison meteorite |
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| Authors: | Michael R Savina Andrew M Davis CEmil Tripa Michael J Pellin Roy S Lewis Roberto Gallino |
| Institution: | 1 Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA 2 Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA 3 Department of the Geophysical Sciences, Chicago, IL 60637, USA 4 Department of Chemistry, University of Chicago, Chicago, IL 60637, USA 5 Laboratory for Space Sciences, Washington University, St. Louis, MO 63130, USA 6 Dipartimento di Fisica Generale, Università di Torino and Sezione INFN di Torino, I-10125 Torino, Italy 7 Institute of Astronomy, Cambridge University, Madingley Road, Cambridge CB3 0HA, United Kingdom |
| Abstract: | Barium isotopic compositions of single 2.3-5.3 μm presolar SiC grains from the Murchison meteorite were measured by resonant ionization mass spectrometry. Mainstream SiC grains are enriched in s-process barium and show a spread in isotopic composition from solar to dominantly s-process. In the relatively coarse grain size fraction analyzed, there are large grain-to-grain variations of barium isotopic composition. Comparison of single grain data with models of nucleosynthesis in asymptotic giant branch (AGB) stars indicates that the grains most likely come from low mass carbon-rich AGB stars (1.5 to 3 solar masses) of about solar metallicity and with approximately solar initial proportions of r- and s-process isotopes. Measurements of single grains imply a wide variety of neutron-to-seed ratios, in agreement with previous measurements of strontium, zirconium and molybdenum isotopic compositions of single presolar SiC grains. |
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