Li-rich RGB stars in the Galactic Bulge

TL;DR

This study measures lithium abundances in a rare sample of 13 K giant stars in the Galactic bulge, revealing potential lithium production during the red giant branch phase with no clear correlation to other elements.

Contribution

First detection of lithium in a small, specific sample of bulge K giants, providing insights into lithium production during stellar evolution.

Findings

13 stars with detectable lithium lines

2 stars with A(Li)>2.7

No correlation between Li abundance and other elements

Abstract

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 detectable Lithium line (6767.18 A) among ~400 stars for which we have spectra in this wavelength range, half of them in Baade's Window (b=-4) and half in a field at b=-6. The stars were observed with the GIRAFFE spectrograph of FLAMES@VLT, with a spectral resolution of R~20,000. Abundances were derived via spectral synthesis and the results are compared with those for stars with similar parameters, but no detectable Li line. We find 13 stars with a detectable Li line, among which 2 have abundances A(Li)>2.7. 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 A(Li)-T_eff correlation. It would seems that there must be a Li production phase during the red giant branch (RGB), acting either on a very short timescale, or selectively only in some stars. The proposed Li production phase 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