Observational signatures for depletion in the Spite plateau: solving the cosmological Li discrepancy?

摘要

We present Li abundances for 73 stars in the metallicity range -3.5 < [Fe/H] < -1.0 using improved IRFM temperatures (Casagrande et al. 2010) with precise E(B-V) values obtained mostly from interstellar NaI D lines, and high-quality equivalent widths (σEw ～ 3%). At all metallicities we uncover a fine-structure in the Li abundances of Spite plateau stars, which we trace to Li depletion that depends on both metallicity and mass. Models including atomic diffusion and turbulent mixing seem to reproduce the observed Li depletion assuming a primordial Li abundance A_(Li) = 2.64 dex (MARLS models) or 2.72 (Kurucz overshooting models), in good agreement with current predictions (A_(Li) = 2.72) from standard BBN. We are currently expanding our sample to have a better coverage of different evolutionary stages at the high and low metallicity ends, in order to verify our findings.