AGB subpopulations in the nearby globular cluster NGC 6397

B. T. MacLean, S. W. Campbell, G. M. De Silva, J. Lattanzio, V. D'Orazi, P. L. Cottrell, Y. Momany, L. Casagrande

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Abstract

It has been well established that Galactic Globular clusters (GCs) harbour more than one stellar population, distinguishable by the anticorrelations of light-element abundances (C–N, Na–O, and Mg–Al). These studies have been extended recently to the asymptotic giant branch (AGB). Here, we investigate the AGB of NGC 6397 for the first time. We have performed an abundance analysis of high-resolution spectra of 47 red giant branch (RGB) and eight AGB stars, deriving Fe, Na, O, Mg, and Al abundances. We find that NGC 6397 shows no evidence of a deficit in Na-rich AGB stars, as reported for some other GCs – the subpopulation ratios of the AGB and RGB in NGC 6397 are identical, within uncertainties. This agrees with expectations from stellar theory. This GC acts as a control for our earlier work on the AGB of M4 (with contrasting results), since the same tools and methods were used.
Original languageEnglish
Pages (from-to)257-265
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Volume475
Issue number1
DOIs
Publication statusPublished - 1 Mar 2018

Bibliographical note

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society, Volume 475, Issue 1, 21 March 2018, Pages 257–265, https://doi.org/10.1093/mnras/stx3217. Copyright 2017 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Keywords

  • stars: abundances
  • stars: AGB and post-AGB
  • Galaxy: abundances
  • Galaxy: formation
  • globular clusters: general

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