Correlation between lithium abundances and ages of solar twin stars

TL;DR

This study investigates the relationship between lithium abundances and ages in solar twin stars, revealing a strong correlation and potential planet engulfment effects, with implications for stellar evolution models.

Contribution

It provides the first detailed empirical correlation between lithium abundance and stellar age in solar twins using high-resolution spectroscopy.

Findings

Li abundance decreases by a factor of ~50 from 1 to 9 Gyr.

Most stars follow the predicted Li depletion models.

Two stars show Li enhancement possibly due to planet engulfment.

Abstract

We want to determine the lithium abundances of solar twin stars as a function of stellar age to provide constraints for stellar evolutions models and to investigate whether there is a connection between low Li abundance and the occurrence of planets. For a sample of 21 solar twins observed with the HARPS spectrograph at high spectral resolution (R~115.000) and very high signal-to-noise ratio (600 < S/N < 2400), precise lithium abundances were obtained by spectral synthesis of the LiI 6707.8 A line and compared to stellar ages, masses, and metallicities determined from a spectroscopic analysis of the same set of HARPS spectra. We show that for the large majority of the solar twins there is a strong correlation between lithium abundance and stellar age. As the age increases from 1 to 9 Gyr, the Li abundance decreases by a factor of ~ 50. The relation agrees fairly well with predictions from non-standard stellar evolution models of Li destruction at the bottom of the upper convection zone. Two stars deviate from the relation by having Li abundances enhanced by a factor of ~ 10, which may be due to planet engulfment. On the other hand, we find no indication of a link between planet hosting stars and enhanced lithium depletion.