Lithium-rich giants in the Galactic thick disk

L. Monaco, S. Villanova, C. Moni Bidin, G. Carraro, D. Geisler, P. Bonifacio, O. A. Gonzalez, M. Zoccali, L. Jilkova

Resultado de la investigación: Contribución a una revistaArtículo

45 Citas (Scopus)

Resumen

Context. Lithium is a fragile element, which is easily destroyed in the stellar interior. The existence of lithium-rich giants still represents a challenge for stellar evolution models. Aims. We have collected a large database of high-resolution stellar spectra of 824 candidate thick-disk giants having 2 MASS photometry and proper motions measured by the Southern Proper-Motion Program (SPM). In order to investigate the nature of Li-rich giants, we searched this database for giants presenting a strong Li I resonance line. Methods. We performed a chemical abundance analysis on the selected stars with the MOOG code along with proper ATLAS-9 model atmospheres. The iron content and atmospheric parameters were fixed by using the equivalent width of a sample of Fe lines. We also derive abundances for C, N, and O and measure or derive lower limits on the 12C/13C isotopic ratios, which is a sensible diagnostic of the stars evolutionary status. Results. We detected five stars with a lithium abundance higher than 1.5, i.e. Li-rich according to the current definition. One of them (SPM-313132) has A(Li) > 3.3 and, because of this, belongs to the group of the rare super Li-rich giants. Its kinematics makes it a likely thin-disk member and its atmospheric parameters are compatible with it being a 4 Ṁ star either on the red giant branch (RGB) or the early asymptotic giant branch. This object is the first super Li-rich giant detected at this phase. The other four are likely low-mass thick-disk stars evolved past the RGB luminosity bump, as determined from their metallicities and atmospheric parameters. The most evolved of them lies close to the RGB-tip. It has A(Li) > 2.7 and a low 12C/13C isotopic ratio, close to the cool bottom processing predictions.

Idioma originalInglés
Número de artículoA90
PublicaciónAstronomy and Astrophysics
Volumen529
DOI
EstadoPublicada - 2011

Áreas temáticas de ASJC Scopus

  • Astronomía y astrofísica
  • Ciencias planetarias y espacial

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    Monaco, L., Villanova, S., Moni Bidin, C., Carraro, G., Geisler, D., Bonifacio, P., Gonzalez, O. A., Zoccali, M., & Jilkova, L. (2011). Lithium-rich giants in the Galactic thick disk. Astronomy and Astrophysics, 529, [A90]. https://doi.org/10.1051/0004-6361/201016285