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American Astronomical Society, Astrophysical Journal, 2(672), p. L115-L118, 2007

DOI: 10.1086/527035

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The double Subgiant Branch of NGC 1851: the role of the CNO abundance

Journal article published in 2007 by S. Cassisi ORCID, M. Salaris, A. Pietrinferni, G. Piotto ORCID, A. P. Milone ORCID, L. R. Bedin ORCID, J. Anderson
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

We explore the possibility that the anomalous split in the Subgiant branch of the galactic globular cluster NGC 1851 is due to the presence of two distinct stellar populations with very different initial metal mixtures: a normal alpha-enhanced component, and one characterized by strong anticorrelations among the CNONa abundances, with a total CNO abundance increased by a factor of two. We test this hypothesis taking into account various empirical constraints, and conclude that the two populations should be approximately coeval, with the same initial He-content. More high-resolution spectroscopical measurements of heavy elements -- and in particular of the CNO sum -- for this cluster are necessary to prove (or disprove) this scenario. ; Comment: 12 pages, 2 figures, ApJ Letter in press