Can Li-rich giants eject shells? Assembling the lithium puzzle in K giants

TL;DR

This paper investigates whether Li-rich K giant stars can eject shells, proposing a model where rapid Li enrichment and depletion lead to shell formation, which can be validated through observations of IR excesses.

Contribution

It introduces a new model linking Li enrichment cycles in K giants to shell ejection, explaining the Li puzzle in stellar evolution.

Findings

Li-rich K giants are associated with IR excesses.

Stars undergo rapid Li enrichment and depletion cycles.

Shell ejection is a key process in Li abundance changes.

Abstract

The existence of K giant stars with high Li abundance continues to challenge the standard theory of stellar evolution. All recent extensive surveys in the Galaxy show the same result: about 1 % of the mainly normal slow rotating K giants are Li rich. We explore here a model with two scenarios based on the important relation of Li-rich and Li-poor K giants with IR excesses. In this model, all K giant stars suffer a rapid enrichment and depletion of Li inducing the formation and ejection of circumstellar shells. The observational detection of these shells will not only validate this model, but also will give important hints on the mechanism of Li enrichment of these stars.