Lithium abundances for 185 main-sequence stars - Galactic evolution and stellar depletion of lithium

摘要

We present a survey of lithium abundances in 185 main- sequence field starswith Teff between 5600 and 6600 K and [Fe/H] from -1.4 to +0.2 based onhigh-resolution spectra of 130 stars and a reanalysis of data from Lambert etal. (1991). The survey takes advantage of improved ways of determiningeffective temperature, metallicity, mass and age, offering an opportunity toinvestigate the behaviour of Li as a function of these parameters. Aninteresting result is the presence of a large gap in the Li-Teff plane, whichdistinguishes `Hyades-like, Li-dip' stars from other stars. These Li-dip starshave a well-defined mass, which decreases with metallicity. Stars above thegap, when divided into four metallicity groups, may show a correlation betweenLi abundance and stellar mass, but with a large dispersion that cannot beexplained by observational errors or differences in metallicity and age, whichranges from 1.5 to 15 Gyr. This suggests that Li depletion occurs early instellar life and that other parameters, e.g. initial rotation velocity and/orthe rate of angular momentum loss, affect the degree of depletion. A comparisonof the distribution of stars in the Li-[Fe/H] plane with evolutionary models ofRomano et al. (1999) suggests that novae are a major source for the Liproduction in the Galactic disk.