First evidence of multiple populations along the AGB from Str\"omgren photometry
Abstract
Spectroscopic studies have demonstrated that nearly all Galactic globular clusters (GCs) harbour multiple stellar populations with different chemical compositions. Moreover, colour-magnitude diagrams based exclusively on Str\"omgrem photometry have allowed us to identify and characterise multiple populations along the RGB of a large number of clusters. In this paper we show for the first time that Str\"omgren photometry is also very effcient at identifying multiple populations along the AGB, and demonstrate that the AGB of M3, M92, NGC362, NGC1851, and NGC6752 are not consistent with a single stellar population. We also provide a catalogue of RGB and AGB stars photometrically identified in these clusters for further spectroscopic follow-up studies.We combined photometry and elemental abundances from the literature for RGB and AGB stars in NGC6752 where the presence of multiple populations along the AGB has been widely debated. We find that, while the MS, SGB, and RGB host three stellar populations with different helium and light element abundances, only two populations of AGB stars are present in the cluster. These results are consistent with standard evolutionary theory.
Keywords
Cite
@article{arxiv.1704.08878,
title = {First evidence of multiple populations along the AGB from Str\"omgren photometry},
author = {Pieter Gruyters and Luca Casagrande and Antonino P. Milone and Simon T. Hodgkin and Aldo Serenelli and Sofia Feltzing},
journal= {arXiv preprint arXiv:1704.08878},
year = {2017}
}
Comments
9 pages, 3 figures, 1 table in the main article, 3 tables in the appendix of which 2 tables containing coordinates and photometry of photometrically identified RGB and AGB stars