Lithium abundances of the local thin disc stars

Abstract

Lithium abundances are presented for a sample of 181 nearby F and G dwarfs with accurate Hipparcos parallaxes. The stars are on circular orbits about the Galactic centre and, hence, are identified as belonging to the thin disc. This sample is combined with two published surveys to provide a catalogue of lithium abundances, metallicities ([Fe/H]), masses, and ages for 451 F-G dwarfs, almost all belonging to the thin disc. The lithium abundances are compared and contrasted with published lithium abundances for F and G stars in local open clusters. The field stars span a larger range in [Fe/H] than the clusters for which [Fe/H] ≃ 0.0 ± 0.2. The initial (i.e. interstellar) lithium abundance of the solar neighbourhood, as derived from stars for which astration of lithium is believed to be unimportant, is traced from log ∈(Li) = 2.2 at [Fe/H] = -1 to log ∈(Li) = 3.2 at +0.1. This form for the evolution is dependent on the assumption that astration of lithium is negligible for the stars defining the relation. An argument is advanced that this latter assumption may not be entirely correct, and, the evolution of lithium with [Fe/H] may be flatter than previously supposed. A sharp Hyades-like Li dip is not seen among the field stars and appears to be replaced by a large spread among lithium abundances of stars more massive than the lower mass limit of the dip. Astration of lithium by stars of masses too low to participate in the Li dip is discussed. These stars show little to no spread in lithium abundance at a given [Fe/H] and mass.