Astronomy Tea Talk

I discuss ongoing measurements of the red giant branch bump in globular clusters and the Galactic bulge, as well as comparisons with models, and how these measurements can be combined to yield a unique probe of the age-metallicity-helium relationship in the bulge. Using the OGLE-III bulge photometric survey, we find that the bulge RGBB may indicate a much higher level of helum enrichment than that observed in globular clusters, closer to Y~0.31 than Y~0.27 for stars at solar metallicity. In addition, I discuss how the Bump parameters are distinct toward double-clump sightlines, implying the presence of a helium gradient corresponding to the metallicity gradient.