The helium content of globular clusters: light element abundance correlations and HB morphology

摘要

Context. In the context of the multiple stellar population scenario in globular clusters (GC), helium (He) has been proposed as thekey element to interpret the observed multiple main sequences (MS), subgiant branches (SGB) and red giant branches (RGB), as well as the complex horizontal branch (HB) morphology. However, up to now, He has never been directly measured in GC stars (8500 < Teff < 11 500 K) to verify this hypothesis.