A sequence of nitrogen-rich very red giants in the globular cluster NGC 1851

Eugenio Carretta, Valentina D'Orazi, Raffaele G. Gratton, Sara Lucatello

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Abstract

We present the abundances of N in a sample of 62 stars on the red giant branch (RGB) in the peculiar globular cluster NGC 1851. The values of [N/Fe] ratio were obtained by comparing the flux measured in the observed spectra with that from synthetic spectra for up to about 15 features of CN. This is the first time that N abundances are obtained for such a large sample of RGB stars from medium-resolution spectroscopy in this cluster. With these abundances, we provide chemical tagging of the split RGB found from several studies in NGC 1851. The secondary reddest sequence on the RGB is populated almost exclusively by N-rich stars, confirming our previous suggestion based on Strömgren magnitudes and colours. These giants are also, on average, enriched in s-process elements such as Ba, and are likely the results of pollution from low-mass stars that experienced episodes of third dredge-up in the asymptotic giant branch phase.

Original languageEnglish
Article numberA32
Pages (from-to)1-5
Number of pages5
JournalAstronomy and Astrophysics
Volume563
DOIs
Publication statusPublished - Mar 2014

Bibliographical note

Copyright ESO 2014. First published in Astronomy and astrophysics 563, A32, 2014, published by EDP Sciences. The original publication is available at http://doi.org/10.1051/0004-6361/201323023

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