Lithium Detection in Red Supergiant Stars of the Perseus Complex

Abstract

We present the first systematic study of lithium abundance in a chemically homogeneous sample of 27 red supergiants (RSGs) in the young Perseus complex. For these stars, accurate stellar parameters and detailed chemical abundances of iron and iron peak, CNO, alpha, light, and neutron capture elements have already been obtained by means of high-resolution optical and near-infrared spectroscopy. The observed RSGs have half-solar metallicity, 10–30 Myr ages, bolometric luminosities in the 104–105 L ⊙ range, and likely mass progenitors in the 9–14 M ⊙ range. We detected the optical Li i doublet in eight out of the 27 observed K- and M-type RSGs, finding relatively low A(Li) < 1.0 dex abundances, while for the remaining 19 RSGs upper limits of A(Li) < –0.2 dex have been set. Warmer and less luminous (i.e., likely less massive) as well as less mixed (i.e., with lower [C/N] and 12C/13C depletion) RSGs with Li detection show somewhat higher Li abundances. In order to explain the Li detection in ∼30% of the observed RSGs, we speculate that some stochasticity should be at work, in a scenario where the Li was not completely destroyed in the convective atmospheres and/or a secondary production took place during the post-main-sequence evolution.