Evidence for a range of metallicities in the parent stars of presolar SiC grains

摘要

The majority of presolar SiC grains present in primitive meteorites have been identified to condense from the winds of C-rich AGE stars. The Si isotopic ratios of three types (mainstream, Y and Z grains) can be used to obtain information about the metallicity of their parent stars. Single grain data and results from nucleosynthetic calculations indicate that mainstream grains are from stars of close-to-solar metallicity, grains of type Y from stars with metallicity Z approximate to 0.01 and grains of type Z from stars with Z approximate to 0.006. These results in turn suggest that the Galactic evolution of the Si-29,Si-30/Si-28 ratios shortly before and at solar system formation was slower than previously believed. [References: 13]