Vol. 543
In section 5. Galactic structure, stellar clusters and populations

Two distinct halo populations in the solar neighborhood. IV. Lithium abundances.

by P.E. Nissen and W.J. Schuster, A&A 543, A28

In a previous study, these authors have shown that there are two populations of halo stars in the Milky Way with distinctly different alpha-element abundances for the same range in metallicity, [Fe/H]. This difference has been suggested to be caused by a different origin of these two groups of stars: high-alpha stars were formed in situ, and low-alpha stars have been accreted from satellite galaxies. In this paper the authors use NOT/FIES and VLT/UVES spectra to measure lithium abundances in the range -1.4 < [Fe/H]< -0.7. They find no significant differences between the two populations. The stars seem to have been formed with a lithium abundance close to the primordial value predicted by standard Big Bang nucleosynthesis calculations based on the WMAP baryon density, and the actual value is consistent with a depletion in time that is approximately linearly dependent upon stellar mass and heavy-element abundance. This is not the case for more metal-poor stars. The lack of difference in lithium abundance between the two groups of halo stars suggests that environmental effects do not play an important role in the destruction of lithium.