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

TL;DR

This study measures lithium abundances in metal-poor stars, revealing a metallicity- and mass-dependent depletion pattern that aligns with Big Bang nucleosynthesis predictions, potentially resolving the cosmological lithium discrepancy.

Contribution

It provides detailed lithium abundance measurements across a range of metallicities using improved temperature and reddening estimates, and models Li depletion considering atomic diffusion and turbulent mixing.

Findings

Li depletion varies with metallicity and mass.

Observed Li abundances align with standard BBN predictions.

Models including atomic diffusion reproduce the depletion pattern.

Abstract

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 (errors ~ 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 ALi = 2.64 dex (MARCS models) or 2.72 (Kurucz overshooting models), in good agreement with current predictions (ALi = 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.