We present the YBC database of stellar bolometric corrections (BCs), available at http://stev.oapd.inaf.it/YBC. We homogenise widely-used theoretical stellar spectral libraries and provide BCs for many popular photometric systems, including the Gaia filters. The database can be easily extended to additional photometric systems and stellar spectral libraries. The web interface allows users to transform their catalogue of theoretical stellar parameters into magnitudes and colours of selected filter sets. The BC tables can be downloaded or also be implemented into large simulation projects using the interpolation code provided with the database. We compute extinction coefficients on a star-by-star basis, hence taking into account the effects of spectral type and nonlinearity dependency on the total extinction. We illustrate the use of these BCs in PARSEC isochrones. We show that using spectral-type dependent extinction coefficients is quite necessary for Gaia filters whenever A V 0.5 mag. BC tables for rotating stars and tables of limb-darkening coefficients are also provided.

In this work, we study the Galactic evolution of lithium by means of chemical evolution models in the light of the most recent spectroscopic data from Galactic stellar surveys. We consider detailed chemical evolution models for the Milky Way halo, discs and bulge, and we compare our model predictions with the most recent spectroscopic data for these different Galactic components. In particular, we focus on the decrease of lithium at high metallicity observed by the AMBRE Project, the Gaia-ESO Survey, and other spectroscopic surveys, which still remains unexplained by theoretical models. We analyse the various lithium producers and confirm that novae are the main source of lithium in the Galaxy, in agreement with other previous studies. Moreover, we show that, by assuming that the fraction of binary systems giving rise to novae is lower at higher metallicity, we can suggest a novel explanation to the lithium decline at supersolar metallicities: the above assumption is based on independent constraints on the nova system birthrate, that have been recently proposed in the literature. As regards to the thick disc, it is less lithium enhanced due to the shorter timescale of formation and higher star formation efficiency with respect to the thin disc and, therefore, we have a faster evolution and the "reverse knee" in the A(Li) vs. [Fe/H] relation is shifted towards higher metallicities. Finally, we present our predictions about lithium evolution in the Galactic bulge, that, however, still need further data to be confirmed or disproved.

Lithium abundance derived in metal-poor main sequence stars is about three times lower than the value of primordial Li predicted by the standard Big Bang nucleosynthesis when the baryon density is taken from the CMB or the deuterium measurements. This disagreement is generally referred as the lithium problem. We here reconsider the stellar Li evolution from the pre-main sequence to the end of the main sequence phase by introducing the effects of convective overshooting and residual mass accretion. We show that 7 Li could be significantly depleted by convective overshooting in the premain sequence phase and then partially restored in the stellar atmosphere by a tail of matter accretion which follows the Li depletion phase and that could be regulated by EUV photo-evaporation. By considering the conventional nuclear burning and microscopic diffusion along the main sequence we can reproduce the Spite plateau for stars with initial mass m 0 = 0.62 − 0.80 M ⊙ , and the Li declining branch for lower mass dwarfs, e.g, m 0 = 0.57 − 0.60 M ⊙ , for a wide range of metallicities (Z=0.00001 to Z=0.0005), starting from an initial Li abundance A(Li) = 2.72. This environmental Li evolution model also offers the possibility to interpret the decrease of Li abundance in extremely metal-poor stars, the Li disparities in spectroscopic binaries and the low Li abundance in planet hosting stars.