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

Research output: Contribution to journalArticle

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 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.

Details

Authors
  • 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
Organisations
External organisations
  • INAF - Osservatorio Astrofisico di Arcetri
  • Agenzia Spaziale Italiana (ASI) Science Data Center
  • INAF Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna
  • University of Geneva
  • University of Toulouse
  • Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences
  • Peking University
  • University of Burgundy - Franche-Comté
  • Vilnius University
  • Uppsala University
  • University of Valparaíso
  • Max Planck Institute for Astronomy
  • University of Padova
  • University of Bologna
  • Observatoire de Besancon
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology

Keywords

  • Globular clusters: individual: NGC 1261, Stars: chemically peculiar, Surveys, Techniques: spectroscopic
Original languageEnglish
Article numberL2
JournalAstronomy and Astrophysics
Volume639
Publication statusPublished - 2020
Publication categoryResearch
Peer-reviewedYes