Concerning Li-rich status of KIC~9821622: A Kepler field RGB star reported as Li-rich Giant

TL;DR

This study reanalyzed the Li-rich classification of KIC 9821622, a unique RGB star, finding its lithium abundance to be normal for its evolutionary stage, thus clarifying the origin of Li enhancement in such stars.

Contribution

The paper provides a revised lithium abundance measurement for KIC 9821622, challenging previous classifications and supporting the idea that Li enhancement occurs during the He-flash phase.

Findings

Li abundance is lower than previously reported.

KIC 9821622's Li level is typical for red giants.

Li enhancement likely occurs during He-flash at RGB tip.

Abstract

Given the implications for the origin of Li enhancement in red giants we have reviewed Li-rich classification of KIC~9821622, the only bonafide RGB giant with He inert-core till date, reported as a Li-rich giant by reanalyzing the high-resolution spectra. We have obtained $A(Li)_{LTE} = 1.42 \pm 0.05$ dex. After correcting for non-LTE it is $A(Li)_{NLTE} = 1.57 \pm 0.05 $ dex which is significantly less than the reported A(Li) = $1.80 \pm 0.2$~dex. We found the sub-ordinate line at 6103 \AA\ is too weak or absent to measure Li abundance. The derived abundance is normal for red giants undergoing dilution during the 1st dredge-up. Since all the known Kepler field Li-rich giants belong to the red clump region, this clarification removes the anomaly and strengthens the evidence that the Li enhancement in low mass giants may be associated only with the He-core burning phase. The Li excess origin, probably, lies during He-flash at the RGB tip, an immediate preceding phase to red clump.