Li-rich red giant branch stars in the Galactic bulge

¹ Departamento Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860 Stgo., Chile e-mail: oagonzal@uc.cl; [mzoccali;Dante]@astro.puc.cl
² European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
³ Departamento Ciencias Físicas y Astronómicas, Universidad de Concepción, Concepción, Chile
⁴ Université de Nice Sophia Antipolis, CNRS, Observatoire de la Côte d'Azur, BP 4229, 06304 Nice Cedex 4, France
⁵ INAF-Osservatorio Astronomico di Teramo, via M. Maggini, 64100 Teramo, Italy
⁶ Specola Vaticana, V00120 Citta del Vaticano, Italy
⁷ INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy
⁸ Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, São Paulo 05508-900, Brazil
⁹ Università di Padova, Dipartimento di Astronomia, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
¹⁰ Observatoire de Paris-Meudon, 92195 Meudon Cedex, France 

Received: 11 May 2009
Accepted: 9 July 2009

Abstract

Aims. We present lithium abundance determination for a sample of K giant stars in the Galactic bulge. The stars presented here are the only 13 stars with a detectable lithium line (6767.18 Å) among ~400 stars for which we have spectra in this wavelength range, half of them in Baade's Window () and half in a field at .

Methods. The stars were observed with the GIRAFFE spectrograph of FLAMES mounted on VLT, with a spectral resolution of . Abundances were derived from spectral synthesis and the results are compared with those of stars with similar parameters, but no detectable Li line.

Results. We find 13 stars with a detectable Li line, among which 2 have abundances . No clear correlations were found between the Li abundance and those of other elements. With the exception of the two most Li  rich stars, the others follow a fairly tight correlation.

Conclusions. There is strong indication of a Li production phase during the red giant branch (RGB), acting either on a very short timescale, or selectively only in some stars. That the proposed Li production phase is associated with the RGB bump cannot be excluded, although our targets are significantly brighter than the predicted RGB bump magnitude for a population at 8 kpc.