Chemical abundances in bright giants of the globular cluster M62 (NGC 6266)

• Main Author: Yong, David
• Publication Date: 2014
• Other Authors: Alves-Brito, Alan, Da Costa, Gary Stewart, Alonso Garcia, Javier, Karakas, Amanda I., Pignatari, Marco, Roederer, Ian U., Aoki, Wako, Fishlock, Cherie K., Grundahl, Frank, Norris, John E.
• Format: Article
• Language: eng
• Source: Repositório Institucional da UFRGS
• Download full: http://hdl.handle.net/10183/103450
• topic: Composicao estelar; Estrelas gigantes; Aglomerados estelares globulares; Massa estelar; Rotacao estelar; Stars: abundances; Galaxy: abundances; Globular clusters: individual: NGC 6266

With the exception of Terzan 5, all the Galactic globular clusters that possess significant metallicity spreads, such as ω Cen and M22, are preferentially the more luminous clusters with extended horizontal branches. Here we present radial velocities and chemical abundances for seven bright giants in the globular cluster M62, a previously little-studied cluster. With MV = −9.18, M62 is the ninth most luminous Galactic globular cluster and has an extended horizontal branch. Within our sample, we find (i) no evidence for a dispersion in metallicity, [Fe/H], beyond the measurement uncertainties, (ii) star-to-star abundance variations for C, O, Na and Al with the usual correlations between these elements as seen in other globular clusters, and (iii) a global enrichment for the elements Zr, Ba and La at the level [X/Fe] − ~ +0.4 dex. For elements heavier than La, the abundance ratios are consistent with the scaled-solar r-process distribution. Below La, the abundances are anomalous when compared to the scaled-solar s-process or r-process distributions. For these elements, the abundance signature in M62 is in agreement with predictions of the s-process from fast-rotating massive stars, although the high [Rb/Y] ratio we measure may be a challenge to this scenario.