Discovery of Nine Super Li-rich Unevolved Stars from the LAMOST Survey

TL;DR

This paper reports the discovery of nine unevolved stars with extremely high lithium levels from the LAMOST survey, suggesting recent lithium enrichment possibly due to circumstellar matter accretion.

Contribution

First identification of nine super Li-rich unevolved stars with unprecedented lithium levels using LAMOST medium-resolution spectra.

Findings

Nine super Li-rich unevolved stars discovered.

Seven stars are fast rotators with high vsini.

Lithium enrichment likely due to circumstellar matter accretion.

Abstract

Based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) medium-resolution spectroscopic survey (MRS), we report the discovery of nine super Li-rich unevolved stars with A(Li) $>$ 3.8 dex. These objects show unusually high levels of lithium abundances up to three times higher than the meteoritic value of 3.3 dex, which indicates that they must have experienced a history of lithium enrichment. It is found that seven of our program stars are fast rotators with $vsini>9$ km\,s$^{-1}$, which suggests that the accretion of circumstellar matter may be the main contributor to the lithium enhancement of these unevolved stars, however, other sources cannot be excluded.