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Thomas Bensby. Profile photo.

Thomas Bensby

Senior lecturer

Thomas Bensby. Profile photo.

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

Author

  • N. Sanna
  • E. Franciosini
  • E. Pancino
  • A. Mucciarelli
  • M. Tsantaki
  • C. Charbonnel
  • R. Smiljanic
  • X. Fu
  • A. Bragaglia
  • N. Lagarde
  • G. Tautvaišiene
  • L. Magrini
  • S. Randich
  • T. Bensby
  • A. J. Korn
  • A. Bayo
  • M. Bergemann
  • G. Carraro
  • L. Morbidelli

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

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