期刊
ASTRONOMY & ASTROPHYSICS
卷 639, 期 -, 页码 -出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361/202038435
关键词
surveys; techniques: spectroscopic; stars: chemically peculiar; globular clusters: individual: NGC 1261
资金
- INAF, through the Mainstream Grant [1.05.01.86.22]
- Swedish Research Council [2018-04857]
- project grant The New Milky Way from the Knut and Alice Wallenberg Foundation
- ESO Telescopes at the La Silla Paranal Observatory [188.B-3002, 193.B-0936, 197.B-1074]
- UK Science and Technology Facilities Council
- European Union FP7 programme through ERC [320360]
- Leverhulme Trust [RPG-2012-541]
- INAF
- ESF (European Science Foundation) through the GREAT Research Network Programme
- Ministero dell' Istruzione, dell' Universita' e della Ricerca (MIUR)
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 the Gaia-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 of A(Li)(LTE)=3.92 +/- 0.14, corresponding to A(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, Li-6, C-12/C-13, and several s-process elements is required, as well as detailed modelling of chromospheric activity indicators.
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