Supermassive 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 anticorrelations, were produced by supermassive stars with M ∼ 104 M⊙. Such stars could form in the runaway collisions of massive stars that sank to the cluster centre 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 supermassive stars had lost significant parts of their initial masses when only a small mass fraction of hydrogen, ΔX ∼ 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.