Di Criscienzo, M; D'Antona, Francesca; Milone, Antonino; Ventura, P; Caloi, V; Carini, R; D'Ercole, A; Vesperini, E; Piotto, G
We analyse complementary Hubble Space Telescope and Subaru data for the globular cluster NGC2419. We make a detailed analysis of the horizontal branch (HB), which is composed of two main groups of stars: the luminous blue HB stars, which extend by evolution into the RR Lyrae and red HB region, and a fainter, extremely blue population. We examine the possible models for the latter group and conclude that a plausible explanation is that they correspond to a significant (∼30 per cent) extreme...[Show more]
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