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arXiv · 1911.05243

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

Raghubar Singh·Bharat Kumar Yerra·Bacham E. Reddy·Wako Aoki
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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 Å 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.

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Raghubar Singh, Bharat Kumar Yerra, Bacham E. Reddy, Wako Aoki. 2019-11-13. Concerning Li-rich status of KIC~9821622: A Kepler field RGB star reported as Li-rich Giant. https://doi.org/10.1093/mnras%2Fstz3222

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