Abundance Patterns of the S Stars in Centauri
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The abundance of heavy elements has been determined for seven stars in the Galactic globular cluster Cen (NGC 5139). This sample includes five stars classified as S stars by Lloyd Evans, including V6, V17, and ROA 320, which are all variable stars and among the coolest and most luminous stars in the cluster. This study increases the number of S stars in Cen for which high-quality abundance analyses exist to eight. The abundance of post-iron-peak elements supports the hypothesis that the spread in metallicities and heavy-element abundances observed among stars in the cluster is due to chemical self-enrichment of Cen by supernovae and low-mass asymptotic giant branch (AGB) stars. Furthermore, the post-iron-peak elements suggest that the self-enrichment of the cluster was complex and nonhomogeneous with respect to the s-process elements.