Formation and Evolution of Carbon-Enhanced Metal-Poor Stars

Abstract

Very metal-poor stars observed in the Galactic halo constitute a window on the primordial conditions under which the Milky Way was formed. A large fraction of these stars show a great enhancement in the abundance of carbon and other heavy elements. One explanation of this observation is that these stars have undergone mass transfer from an AGB binary companion. This scenario is supported by the evidence that these carbon-enhanced metal-poor (CEMP) stars are mostly found in spectroscopic binary systems. We have started a project with the aim to understand several aspects which still need to be clarified: (1) how the abundances of low-mass metal-poor stars evolve after accretion of material from an evolved asymptotic giant branch star, (2) what the consequences of this mass transfer are for the overall population of CEMP stars, and (3) what its implications are for the initial mass function at early epochs.