The Gaia-ESO Survey: Probing the lithium abundances in old metal-rich dwarf stars in the Solar vicinity

TL;DR

This study investigates how radial migration affects lithium abundances in old, metal-rich dwarf stars near the Sun, showing that their Li levels do not reflect the interstellar medium's Li content, challenging previous assumptions.

Contribution

It demonstrates that Li abundances in old, metal-rich dwarf stars are influenced by stellar migration, indicating they are unreliable proxies for interstellar Li and informing stellar yield models.

Findings

Li abundance in migrated stars is below meteoritic value (<3.26 dex).

Li decreases with increasing [Fe/H] in old dwarf stars (~8 Gyr).

Li in these stars should not be used to estimate interstellar Li abundance.

Abstract

We test a scenario in which radial migration could affect the Li abundance pattern of dwarf stars in the solar neighbourhood. This may confirm that the Li abundance in these stars can not serve as a probe for the Li abundance in the interstellar medium. We use the high-quality data (including Li abundances) from the 6th internal Data Release of the Gaia-ESO survey. In this sample, we group stars by similarity in chemical abundances via hierarchical clustering. Our analysis treats both measured Li abundances and upper limits. The Li envelope of the previously identified radially migrated stars is well below the benchmark meteoritic value (<3.26 dex); the star with the highest detected abundance has A(Li) = 2.76 dex. This confirms the previous trends observed for old dwarf stars (median ages $\sim$ 8 Gyr), where Li decreases for [Fe/H]$\gtrsim$0. This result acts as supporting evidence that the abundance of Li measured in the upper envelope of old dwarf stars should not be considered a proxy for the interstellar medium Li. Our scenario also indicates that the stellar yields for [M/H]>0 should not be decreased, as recently proposed in the literature. Our study backs the recent studies that claimed that old dwarfs on the hot side of the dip are efficient probes of the ISM abundance of Li, provided atomic diffusion does not lower significantly the initial Li abundance in the atmospheres of metal-rich objects.