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

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 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
Signaler une correction	Signaler une correction (s'ouvre dans un nouvel onglet)
Identificateur de l’enregistrement	952af64c-06f9-4dbc-8a61-8aa8f96d8380
Enregistrement créé	2016-08-18
Enregistrement modifié	2020-04-22

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