Lithium destruction and production observed in red giant stars

TL;DR

This paper reviews recent observational findings on lithium in evolved red giant stars, highlighting unexpected lithium abundance and its implications for stellar evolution and interstellar medium enrichment.

Contribution

It provides updated observational data on lithium-rich red giants across different evolutionary stages, exploring their origins and potential role in galactic chemical evolution.

Findings

Li-rich giants challenge standard stellar evolution models

Li production observed in AGB stars suggests new nucleosynthesis pathways

Li enrichment may contribute to interstellar medium composition

Abstract

According to standard stellar evolution, lithium is destroyed throughout most of the evolution of low- to intermediate-mass stars. However, a number of evolved stars on the red giant branch (RGB) and the asymptotic giant branch (AGB) are known to contain a considerable amount of Li, whose origin is not always understood well. Here we present the latest development on the observational side to obtain a better understanding of Li-rich K giants (RGB), moderately Li-rich low-mass stars on the AGB, as well as very Li-rich intermediate-mass AGB stars possibly undergoing the standard hot bottom burning phase. These last ones probably also enrich the interstellar medium with freshly produced Li.