Lithium-Rich Field Giants in the Sloan Digital Sky Survey

TL;DR

This study identifies lithium-rich post-main-sequence stars in the Galaxy using SDSS and follow-up spectroscopy, revealing unexpected high lithium levels in evolved stars challenging current stellar evolution models.

Contribution

It reports the discovery of 23 lithium-rich evolved stars and highlights their unexpected evolutionary stages, providing new insights into lithium production in stars.

Findings

23 lithium-rich post-turnoff stars identified

Some stars are on the upper red giant branch and asymptotic giant branch

Challenges existing models of lithium production in evolved stars

Abstract

We present a search for post-main-sequence field stars in the Galaxy with atypically large lithium abundances. Using moderate-resolution spectra taken as part of the Sloan Digital Sky Survey, along with high-resolution followup spectroscopy from the Hobby-Eberly Telescope, we identify 23 post-turnoff stars with log epsilon(Li) greater than 1.95, including 14 with log epsilon(Li) > 2.3 and 8 with log epsilon(Li) > 3.0, well above the low level expected for evolved stars. Comparison with theoretical isochrones indicates that some of our Li-rich stars are affiliated with the upper red giant branch, the asymptotic giant branch and the red clump rather than the RGB bump, which is a challenge to existing models of Li production in evolved stars.