The interplay between super-metallicity, lithium depletion, and radial migration in nearby stars

TL;DR

This study identifies a unique group of old, super-metal-rich dwarf stars with low-eccentricity orbits and lithium depletion, suggesting they formed outside the solar neighborhood and challenging assumptions about lithium as a local ISM proxy.

Contribution

It reveals a new population of super-metal-rich stars with peculiar chemo-dynamical properties and links their lithium depletion to their formation history outside the solar neighborhood.

Findings

Stars are super-metal-rich with low eccentricity orbits.

Lithium abundance is below meteoritic levels.

Stars likely formed outside the solar neighborhood.

Abstract

We report the discovery of a peculiar set of old super-metal-rich dwarf stars with orbits of low eccentricity that reach a maximum height from the Galactic plane between $\sim$ 0.5-1.5 kpc observed by the \emph{Gaia}-ESO Survey. These stars show lithium (Li) depletion, which is anti-correlated with their [Fe/H]. To investigate these stars' chemo-dynamical properties, we used data from the \emph{Gaia}-ESO Survey. We applied hierarchical clustering to group the stars based on their abundances (excluding Li). Orbits were integrated using \emph{Gaia} astrometry and radial velocities from \emph{Gaia}-ESO. Our analysis suggests that the high metallicity of these stars is incompatible with their formation in the solar neighbourhood. We also found that their Li envelope abundance is below the benchmark meteoritic value, in agreement with previous works. This result supports the idea that the Li abundance in old, super-metal-rich dwarf stars should not be considered a proxy for the local interstellar medium Li.