Chemical Abundances of CH Stars in Omega Centauri

Abstract

Omega Centauri (hereafter Omega Cen), the largest globular cluster in the Galaxy, is an important environment for studying nucleosynthesis because of its significant abundance variations and evidence of multiple stellar generations. The cluster also contains several known CH stars, which are thought to be the result of past binary mass transfer from an asymptotic giant branch (AGB) companion. CH stars are thus hypothesized to be a good probe of AGB nucleosynthesis. We use the CH stars in Omega Cen to test this assumption. We compare the elemental abundances of CH stars within the cluster to those of CH stars outside the cluster to test the effects of the formation environment on the abundances of AGB nucleosynthesis products. We also compare the chemical abundances of the Omega Cen CH stars to other red giants in the cluster to determine if the same processes are responsible for the chemical enrichment of both the CH stars and the cluster. In general, we find that the CH stars in Omega Cen have similar abundances to CH stars in the field. We also find that as metallicity increases, the s-process abundances of stars in Omega Cen approach those of the CH stars, indicating that similar mechanism is responsible for the enrichment in both cases.