The bi-modal $^7$Li distribution of the Milky Way's thin-disk dwarf stars: The role of Galactic-scale events and stellar evolution

TL;DR

This study reveals a bi-modal lithium abundance distribution in Milky Way thin-disk stars, linking it to Galactic star formation history and stellar evolution processes, and suggests A(Li) as a proxy for galactic evolution.

Contribution

It demonstrates that the bi-modal A(Li) distribution in thin-disk stars results from specific star formation history and stellar evolution, highlighting the role of Galactic-scale events.

Findings

Bi-modal A(Li) distribution confirmed in thin-disk FGK stars

Bi-modality linked to Milky Way star formation history

A(Li) evolution serves as a proxy for galactic evolution

Abstract

The lithium abundance, A(Li), in stellar atmospheres suffers from various enhancement and depletion processes during the star's lifetime. While several studies have demonstrated that these processes are linked to the physics of stellar formation and evolution, the role that Galactic-scale events play in the galactic A(Li) evolution is not yet well understood. We aim to demonstrate that the observed A(Li) bi-modal distribution, in particular in the FGK-dwarf population, is not a statistical artefact and that the two populations connect through a region with a low number of stars. We also want to investigate the role that Galactic-scale events play in shaping the A(Li) distribution of stars in the thin disk. We use statistical techniques along with a Galactic chemical evolution model for A(Li) that includes most of the well-known $^7$Li production and depletion channels. We confirm that the FGK main-sequence stars belonging to the Milky Way's thin disk present a bi-modal A(Li) distribution. We demonstrate that this bi-modality can be generated by a particular Milky Way star formation history profile combined with the stellar evolution's $^7$Li depletion mechanisms. We show that A(Li) evolution can be used as an additional proxy for the star formation history of our Galaxy.