Lithium Abundance of Halo Dwarfs Revised

Lithium abundances in a sample of halo dwarfs have been redetermined by using the new Teff derived by Fuhrmann et al (1994) from modelling of the Balmer lines. These Teff are reddening independent, homogeneous and of higher quality than those based on broad band photometry. Abundances have been derived by generating new atmospheric models by using the ATLAS-9 code by Kurucz (1993) with enhanced α-elements and without the overshooting option. The revised abundances show a remarkably flat plateau in the LiTeff plane for Teff> 5700 K with no evidence of trend with Teff or falloff at the hottest edge. Li abundances are not correlated with metallicity for [Fe/H]< -1.4 in contrast with Thorburn (1994). All the determinations are consistent with the same pristine lithium abundance and the errors estimated for individual stars fully account for the observed dispersion. The weighted average Li value for the 24 stars of the plateau with Teff> 5700 K and [Fe/H]≤ -1.4, is [Li] = 2.210 ± 0.013, or 2.224 when non-LTE corrections by Carlsson et al (1994) are considered.