Super-Massive Stars as a Source of Abundance Anomalies of Proton-Capture Elements in Globular Clusters

Abstract

We propose that the abundance anomalies of proton-capture elements in globular clusters, such as the C-N, Na-O, Mg-Al and Na-F anti-correlations, were produced by super-massive stars with M ~ 10,000 Msun. Such stars could form in the runaway collisions of massive stars that sank to the cluster center as a result of dynamical friction, or via the direct monolithic collapse of the low-metallicity gas cloud from which the cluster formed. To explain the observed abundance anomalies, we assume that the super-massive stars had lost significant parts of their initial masses when only a small mass fraction of hydrogen, Delta X ~ 0.15, was transformed into helium. We speculate that the required mass loss might be caused by the super-Eddington radiation continuum-driven stellar wind or by the diffusive mode of the Jeans instability.