Institution(s): 1. LJMU
The standard explanation for the origin of the multiple populations in GCs is that of self-enrichment, where stars of a 1st generation expel their stellar ejecta which mixes with primordial material and eventually forms a second (and further) generation of stars. Popular polluting stars are AGBs, fast-rotating massive stars and interacting binaries. By combining measurements of helium, Na, and O from the literature for a sample of GCs, we show that none of the above polluting stars (or combination of them) can explain the observations. The basic problem is that the obsered GCs show similar Na and O-spreads, whereas He varies strongly between clusters, which is incompatible with basic predicitons of nuclear synthesis. Hence, it appears that the basic idea of self-enrichment in GCs can be ruled out, putting the field back to square one.