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Sodium-oxygen anticorrelation among horizontal branch stars in the globular cluster M4

Marino, Anna; Villanova, S; Milone, Antonino; Piotto, G; Lind, Karin; Geisler, D; Stetson, Peter B


The horizontal branch (HB) morphology of globular clusters (GCs) is mainly governed by metallicity. The second parameter problem, well known since the 1960s, states that metallicity alone is not enough to describe the observed HB morphology of many GCs. Despite many efforts to resolve this issue, the second parameter phenomenon still remains without a satisfactory explanation. We have analyzed blue-HB, red-HB, and RR-Lyrae stars in the GC M4 and studied their Fe, Na, and O abundances. Our goal...[Show more]

CollectionsANU Research Publications
Date published: 2011
Type: Journal article
Source: Astrophysical Journal Letters
DOI: 10.1088/2041-8205/730/2/L16
Access Rights: Open Access


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