Grid of stellar models

Recent photometric studies suggest that the He content could vary between the populations of a GC by up to {Delta}He~0.13, in mass fraction. The initial He content impacts the evolution of low-mass stars by ultimately modifying their lifetimes, luminosity, temperatures, and, more generally, the morphology of post-red giant branch (RGB) evolutionary tracks in the Hertzsprung-Russell diagram.

We present new physically accurate isochrones with different initial He enrichments and metallicities, with a focus on the methods implemented to deal with the post-RGB phases. The isochrones are based on tracks computed with the stellar evolution code STAREVOL for different metallicities (Z = 0.0002, 0.0009, 0.002, and 0.008) and with several He enrichments (from 0.248 to 0.600 in mass fraction). We describe the effect of He enrichment on the morphology of the isochrones and we tested these by comparing the predicted number counts of horizontal branch and asymptotic giant branch stars with those of selected GCs.