Spectroscopic study of two new super Li-rich red clump K giants

Abstract

In this paper, we report the discovery of two new super Li-rich K giants: HD 24960 and TYC 1751-1713-1. Based on high-resolution (R ≈ 60 000) spectroscopy, we have derived Li abundance of A(Li) ≈ 4.0 dex for both stars. Other elemental abundances are normal of typical K giants. Low ratios of [C/N] ≤ −0.25 and 12C/13C ≤ 10 suggest that the stars are in the upper red giant branch (RGB) phase. Further, based on Gaia astrometry and secondary calibrations using Kepler asteroseismic and LAMOST spectroscopic data, we argue that both stars belong to the red clump (RC) phase with core He burning. Results add to a half-dozen already known RC Li-rich K giants and support the growing evidence that the origin of Li excess in RC giants seems to be associated with either He flash at the tip of the RGB or recent planet/ brown dwarf merger events closer to the RGB tip.