Nataf, David; Gould, A; Pinsonneault, Marc H; Stetson, Peter B
We combine ground- and space-based photometry of the Galactic globular cluster 47 Tuc to measure four independent lines of evidence for a helium gradient in the cluster, whereby stars in the cluster outskirts would have a lower initial helium abundance than stars in and near the cluster core. For our first and second lines of evidence, we show that the red giant branch bump stars exhibit gradients in their number counts and brightness. With increased separation from the cluster center, they...[Show more]
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