Di Criscienzo, M; Tailo, Marco; Milone, Antonino; D'Antona, Francesca; Ventura, P; Dotter, Aaron; Brocato, E.
We use images acquired with the Hubble Space Telescope Wide Field Camera 3 and new models to probe the horizontal branch (HB) population of the Galactic globular cluster (GC) NGC 2419. A detailed analysis of the composite HB highlights three populations: (1) the blue luminous HB, hosting standard helium stars (Y = 0.25) with a very small spread of mass; (2) a small population of stars with intermediate helium content (0.26 < Y ≲ 0.29); and (3) the well-populated extreme HB. We can fit the last...[Show more]
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