2016/09/30 by S. Villanova, C. Moni Bidin, F. Mauro +3 · 1 citation
Chemistry · Physics and Astronomy · #Abundance (ecology) #Astro and Planetary Science #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Chemistry #Cluster (spacecraft) #Galaxy #Globular cluster #Halo #Metal #Metallicity #Physics #Population #Red-giant branch #Spectral line #Stars #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stw2509
13 pages, 14 figures, accepted for publication on MNRAS. arXiv admin note: text overlap with arXiv:1605.03408
openalex publication_date 2016/09/30 · arxiv created 2016/10/06 · arxiv updated 2016/10/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present the abundance analysis for a sample of 17 red giant branch stars in the metal-poor globular cluster M28 based on high-resolution spectra. This is the first extensive spectroscopic study of this cluster. We derive abundances of O, Na, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Ba, La, Ce, and Eu. We find a metallicity of [Fe/H] = −1.29 ± 0.01 and an α-enhancement of +0.34 ± 0.01 (errors on the mean), typical of halo globular clusters in this metallicity regime. A large spread is observed in the abundances of light elements O, Na, and Al. Mg also shows an anti-correlation with Al with a significance of 3σ. The cluster shows a Na–O anti-correlation and a Na–Al correlation. This correlation is not linear but ‘segmented’ and that the stars are not distributed continuously, but form at least three well-separated sub-populations. In this aspect, M28 resembles NGC 2808 that was found to host at least five sub-populations. The presence of a Mg–Al anti-correlation favour massive AGB stars as the main polluters responsible for the multiple-population phenomenon.