文章基本信息

标题：The Gaia-ESO Survey: an extremely Li-rich giant in globular cluster NGC 1261 ⋆
本地全文：下载
作者：N. Sanna ; E. Franciosini ; E. Pancino 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2020
卷号：639
页码：1-5
DOI：10.1051/0004-6361/202038435
语种：English
出版社：EDP Sciences
摘要：Lithium-rich stars in globular clusters are rare. Only 14 have been found so far, in different evolutionary phases from dwarfs to giants. Different mechanisms have been proposed to explain this enhancement, but it is still an open problem. Using spectra collected within theGaia-ESO Survey, obtained with the GIRAFFE spectrograph at the ESO Very Large Telescope, we present the discovery of the first Li-rich star in the cluster NGC 1261, the second star known in the red giant branch bump phase. The star shows an extreme Li overabundance ofA(Li)LTE = 3.92 ± 0.14, corresponding toA(Li)NLTE = 3.40 dex. We propose that the Li enhancement is caused by fresh Li production through an extra mixing process (sometimes referred to as cool bottom burning). Alternatively, it could be a pre-existing Li overabundance caused by mass-transfer from a red giant star; this mechanism does not enhance the barium abundance and thus we observe low barium. To unambiguously explain the Li enhancement in globular cluster stars, however, a reliable determination of the abundance of key species like Be,6Li,12C/13C, and severals-process elements is required, as well as detailed modelling of chromospheric activity indicators.
关键词：ensurveystechniques: spectroscopicstars: chemically peculiarglobular clusters: individual: NGC 1261