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The Gaia-ESO Survey : An extremely Li-rich giant in globular cluster NGC 1261

Sanna, N. ; Franciosini, E. ; Pancino, E. ; Mucciarelli, A. ; Tsantaki, M. ; Charbonnel, C. ; Smiljanic, R. ; Fu, X. ; Bragaglia, A. and Lagarde, N. , et al. (2020) In Astronomy and Astrophysics 639.
Abstract

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... (More)

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.

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organization
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type
Contribution to journal
publication status
published
subject
keywords
Globular clusters: individual: NGC 1261, Stars: chemically peculiar, Surveys, Techniques: spectroscopic
in
Astronomy and Astrophysics
volume
639
article number
L2
publisher
EDP Sciences
external identifiers
  • scopus:85087924865
ISSN
0004-6361
DOI
10.1051/0004-6361/202038435
project
Gaia-ESO Survey
language
English
LU publication?
yes
id
77543f39-4a69-4f63-beec-37f7ab1113d4
date added to LUP
2020-07-29 13:03:20
date last changed
2024-04-03 10:49:53
@article{77543f39-4a69-4f63-beec-37f7ab1113d4,
  abstract     = {{<p>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.</p>}},
  author       = {{Sanna, N. and Franciosini, E. and Pancino, E. and Mucciarelli, A. and Tsantaki, M. and Charbonnel, C. and Smiljanic, R. and Fu, X. and Bragaglia, A. and Lagarde, N. and Tautvaišiene, G. and Magrini, L. and Randich, S. and Bensby, T. and Korn, A. J. and Bayo, A. and Bergemann, M. and Carraro, G. and Morbidelli, L.}},
  issn         = {{0004-6361}},
  keywords     = {{Globular clusters: individual: NGC 1261; Stars: chemically peculiar; Surveys; Techniques: spectroscopic}},
  language     = {{eng}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{The Gaia-ESO Survey : An extremely Li-rich giant in globular cluster NGC 1261}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/202038435}},
  doi          = {{10.1051/0004-6361/202038435}},
  volume       = {{639}},
  year         = {{2020}},
}