The AMBRE Project: Constraining the lithium evolution in the Milky Way
  The chemical evolution of lithium in the Milky Way represents a major problem
in modern astrophysics. Indeed, lithium is, on the one hand, easily destroyed
in stellar interiors, and, on the other hand, produced at some specific stellar
evolutionary stages that are still not well constrained. The goal of this paper
is to investigate the lithium stellar content of Milky Way stars in order to
put constraints on the lithium chemical enrichment in our Galaxy, in particular
in both the thin and thick discs. Thanks to high-resolution spectra from the
ESO archive and high quality atmospheric parameters, we were able to build a
massive and homogeneous catalogue of lithium abundances for 7300 stars derived
with an automatic method coupling, a synthetic spectra grid, and a Gauss-Newton
algorithm. We validated these lithium abundances with literature values,
including those of the Gaia benchmark stars. In terms of lithium galactic
evolution, we show that the interstellar lithium abundance increases with
metallicity by 1 dex from [M/H]=-1 dex to +0.0 dex. Moreover, we find that this
lithium ISM abundance decreases by about 0.5 dex at super-solar metalllicity.
Based on a chemical separation, we also observed that the stellar lithium
content in the thick disc increases rather slightly with metallicity, while the
thin disc shows a steeper increase. The lithium abundance distribution of
alpha-rich, metal-rich stars has a peak at A(Li)~3 dex. We conclude that the
thick disc stars suffered of a low lithium chemical enrichment, showing lithium
abundances rather close to the Spite plateau while the thin disc stars clearly
show an increasing lithium chemical enrichment with the metallicity, probably
thanks to the contribution of low-mass stars.
