Presolar SIC grains and their parent stars

Details Presolar SIC grains and their parent stars Presolar SIC grains and their parent stars

Jul 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998m%26ps...33..871l&link_type=abstract

Meteoritics & Planetary Science, vol. 33, no. 4, pp. 871-880.

Computer Science

20

Scientific paper

Carbon stars are an important source of presolar TiC, SiC, and graphite grains found in meteorites. The elemental abundances in the stellar sources of the SiC grains are inferred using condensation calculations. These elemental abundances together with carbon isotopic compositions are used to identify possible groups of carbon stars which may have contributed SiC grains to the presolar dust cloud. The most likely parent stars of meteoritic SiC mainstream grains are N type carbon stars and evolved subgiant CH stars, which both have s-process element abundances higher than solar and 10 < 12C/13C <100. The J stars and giant CH stars, with solar and greater than solar abundances of s-process elements, respectively, are good candidate parents for the 'A' and 'B' SiC grains with low 12C/13C ratios. A special subgroup of CH giant stars with very large 12C/13C ratios could have parented the 'Y' SiC grains with 12C/13C ratios >100. The carbon star population (e.g., N, R, J, CH groups) needed to provide the observed SiC grains is compared to the current population of carbon stars. This comparison suggests that low metallicity CH stars may have been more abundant in the past (>4.5 Gyrs ago) than at present. This suggestion is also supported by condensation chemistry modeling of the trace element patterns in the SiC grains which shows that subsolar iron abundances may be required in the stellar sources for many SiC grains. The results of this study suggest that presolar SiC grains in meteorites can provide information about carbon stars during galactic evolution.

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