AGB subpopulations in the nearby globular cluster NGC 6397

Abstract

It has been well established that Galactic Globular clusters (GCs) harbour more than one stellar population, distinguishable by the anti-correlations 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 RGB and 8 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 M 4 (with contrasting results), since the same tools and methods were used.

10 pages, 7 figures, 8 tables (2 online-only). Accepted for publication in MNRAS

References in corpus (29)

• Astrophysics Source Code Library
• The GALAH Survey: Scientific Motivation
• A new implementation of the infrared flux method using the 2MASS catalogue
• The ACS Survey of Galactic Globular Clusters. III. The Double Subgiant Branch of NGC 1851
• ARES v2 - new features and improved performance
• Chemical tagging with APOGEE: Discovery of a large population of N-rich stars in the inner Galaxy
• Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. III. A quintuple stellar population in NGC2808
• Non-LTE aluminium abundances in late-type stars
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. II. The seven stellar populations of NGC7089 (M2)
• Non-LTE oxygen line formation in 3D hydrodynamic model stellar atmospheres
• Detection of solar-like oscillations in relics of the Milky Way: asteroseismology of K giants in M4 using data from the NASA K2 mission
• Mg line formation in late-type stellar atmospheres: II. Calculations in a grid of 1D models
• AGB Sodium Abundances in the Globular Cluster 47 Tucanae (NGC 104)
• O and Na abundance patterns in open clusters of the Galactic disk
• Photometry and spectroscopy of multiple populations along the AGB of NGC2808 and NGC6121 (M4)
• O, Na, Ba and Eu abundance patterns in open clusters
• Clear evidence for the presence of second-generation asymptotic giant branch stars in metal-poor Galactic globular clusters
• Chemical analysis of Asymptotic Giant Branch stars in M62
• On the missing second generation AGB stars in NGC6752
• Sodium abundances of AGB and RGB stars in Galactic globular clusters II. Analysis and results of NGC 104, NGC 6121 and NGC 6809
• An extreme paucity of second population AGB stars in the normal globular cluster M4
• Sodium abundances of AGB and RGB stars in galactic globular clusters I. Analysis and results of NGC 2808
• Lost and found: evidence of Second Generation stars along the Asymptotic Giant Branch of the globular cluster NGC 6752
• Multiple populations along the asymptotic giant branch of the globular cluster M 4
• Are there any first-generation stars in globular clusters today?
• Evolution of long-lived globular cluster stars. II. Sodium abundance variations on the asymptotic giant branch as a function of globular cluster age and metallicity
• First evidence of multiple populations along the AGB from Strömgren photometry
• NGC 6752 AGB Stars Revisited: I. Improved AGB temperatures remove apparent overionisation of Fe I

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• A combined study of thermohaline mixing and envelope overshooting with PARSEC: Calibration to NGC 6397 and M4
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