Detection of Lithium in a Main Sequence Bulge Star Using Keck I as a 15m Diameter Telescope

Abstract

The bulge contains the most chemically evolved old stellar population in the Milky Way. Thanks to microlensing, it is now possible to obtain high resolution echelle spectra of bulge stars near the main sequence turn-off, and study the abundance of elements that are affected by stellar evolution, such as lithium. We have observed with the HIRES spectrograph on the Keck I 10m telescope the source star of the MACHO microlensing event 97BLG45 while it was magnified by about 1 magnitude. Here we report the detection of the Li I line at λ6707.8 à in the echelle spectrum of this star, and measure the bulge lithium abundance for the first time: A(Li) = 2.25 \pm 0.25.

10 pages, 2 PostScript figures, uses aaspp4.sty. Submitted to The Astrophysical Journal Letters