Understanding AGB Nucleosynthesis from Chemical Composition Studies of CH Stars

Abstract

CH stars are known to show enhanced abundances of carbon and heavy s-process elements. They are metal-deficient population II objects. Their luminosities indicate that they are mostly giants; hence, the observed enhanced abundances of heavy elements are unlikely to have been produced inside the stars during stellar nucleosynthesis. As most of the CH stars are known to be binaries, the observed abundance anomalies are generally explained on the basis of a binary picture involving a low-mass companion evolving through the AGB phase. Detailed chemical analysis of CH stars can thus provide knowledge about the nucleosynthesis taking place in the companion AGB stars. We have conducted a detailed chemical composition study for a large sample of CH stars. Interpretation of the elemental abundances based on AGB nucleosynthesis models will help to understand the origin of the heavy elements observed in these objects.