A chemical trompe-l’oeil: no iron spread in the globular cluster N22

Par Conseil national de recherches du Canada

DOI	Trouver le DOI : https://doi.org/10.1088/0004-637X/809/2/128
Auteur	Rechercher : Mucciarelli, A.; Rechercher : Lapenna, E.; Rechercher : Massari, D.; Rechercher : Pancino, E.; Rechercher : Stetson, P. B.¹; Rechercher : Ferraro, F. R.; Rechercher : Lanzoni, B.; Rechercher : Lardo, C.
Affiliation	Conseil national de recherches du Canada. Infrastructure scientifique nationale
Format	Texte, Article
Sujet	stars: abundances; techniques: spectroscopic
Résumé	We present the analysis of high-resolution spectra obtained with UVES and UVES-FLAMES at the Very Large Telescope of 17 giants in the globular cluster (GC) M22, a stellar system suspected to have an intrinsic spread in iron abundance. We find that when surface gravities are derived spectroscopically (in order to obtain the same iron abundance from Fe I and Fe II lines) the [Fe/H] distribution spans ∼0.5 dex, according to previous analyses. However, the gravities obtained in this way correspond to unrealistically low stellar masses (0.1–0.5 M) for most of the surveyed giants. Instead, when photometric gravities are adopted, the [Fe II/H] distribution shows no evidence of spread, in variance with the [Fe I/H] distribution. This difference has been recently observed in other clusters and could be due to non-local thermodynamical equilibrium effects driven by over-ionization mechanisms that mainly affect the neutral species (thus providing lower [Fe I/H]), but leave [Fe II/H] unaltered. We confirm that the s-process elements show significant star-to-star variations and their abundances appear to be correlated with the difference between [Fe I/H] and [Fe II/H]. This puzzling finding suggests that the peculiar chemical composition of some cluster stars may be related to effects able to spuriously decrease [Fe I/H]. We conclude that M22 is a GC with no evidence of intrinsic iron spread, ruling out that it has retained the supernovae ejecta in its gravitational potential well.
Date de publication	2015-08-20
Maison d’édition	American Astronomical Society IOP Publishing
Dans	The Astrophysical Journal 809, nº 2 : 128–.
Langue	anglais
Publications évaluées par des pairs	Oui
Numéro NPARC	23000653
Exporter la notice	Exporter en format RIS
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Identificateur de l’enregistrement	952af64c-06f9-4dbc-8a61-8aa8f96d8380
Enregistrement créé	2016-08-18
Enregistrement modifié	2020-04-22

Date de modification :: 2024-04-23