Abundance Ratios in Carbon‐Enhanced Metal‐Poor Stars and the Intermediate‐Mass Star Initial Mass Function

Abstract

Star formation in the early Universe proceeded under different conditions than in the present day. A different initial mass function could therefore be expected. While the mass function of the more massive stars may be deduced from their effect on early Galactic chemical evolution, intermediate mass stars live longer, and it is difficult to disentangle their contributions in the pollution of the Galaxy. Binary systems where one star has become an AGB star and transferred mass onto a longer‐lived companion provide an opportunity to observe the nucleosynthesis of the AGB star in detail. Because AGB nucleosynthesis depends on the mass of the AGB star, it may be possible to deduce the mass of the AGB star and therefore place constraints on the mass function of intermediate mass stars. We test the models of AGB nucleosynthesis by observing Li and the 12C/13C ratio in 9 carbon‐rich stars with VLT‐UVES to see if they agree with the mass of AGB stars suggested by the [C/N] ratios previously measured in these stars.