Thomas Bensby
Senior lecturer
The Gaia-ESO Survey : An extremely Li-rich giant in globular cluster NGC 1261
Author
Summary, in English
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, 6Li, 12C/13C, and several s-process elements is required, as well as detailed modelling of chromospheric activity indicators.
Department/s
- Lund Observatory - Has been reorganised
Publishing year
2020
Language
English
Publication/Series
Astronomy and Astrophysics
Volume
639
Document type
Journal article
Publisher
EDP Sciences
Topic
- Astronomy, Astrophysics and Cosmology
Keywords
- Globular clusters: individual: NGC 1261
- Stars: chemically peculiar
- Surveys
- Techniques: spectroscopic
Status
Published
Project
- Gaia-ESO Survey
ISBN/ISSN/Other
- ISSN: 0004-6361