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标题：The discovery of a Li/Na-rich giant star in Omega Centauri: formed from the pure ejecta of super-AGB stars? ★
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作者：A. Mucciarelli ; L. Monaco ; P. Bonifacio 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：623
DOI：10.1051/0004-6361/201834497
语种：English
出版社：EDP Sciences
摘要：We report the discovery of two Li-rich giant stars (fainter than the red giant branch (RGB) bump) in the stellar system Omega Centauri using GIRAFFE-FLAMES spectra. These two stars haveA(Li) = 1.65 and 2.40 dex and they belong to the main population of the system ([Fe/H] = –1.70 and –1.82, respectively). The most Li-rich of them (#25664) has [Na/Fe] = +0.87 dex, which is ~0.5 dex higher than those measured in the most Na-rich stars of Omega Centauri of similar metallicity. The chemical abundances of Li and Na in #25664 can be qualitatively explained by deep extra mixing efficient within the star during its RGB evolution or by super-asymptotic giant branch (AGB) stars with masses between ~7 and 8M⊙. In the latter scenario, this Li/Na-rich star could be formed from the pure ejecta of super-AGB stars before the dilution with pristine material occurs, or, alternatively, be part of a binary system having experienced mass transfer from the companion when this latter evolved through the super-AGB phase. In both these cases, the chemical composition of this unique object could allow to look for the first time at the chemical composition of the gas processed in the interior of super-AGB stars.
关键词：Key wordsenstars: abundancestechniques: spectroscopicglobular clusters: individual: Omega Centauri