Identifying Li-rich giants from low-resolution spectroscopic survey

Abstract

In this paper we discuss our choice of a large unbiased sample used for the survey of red giant branch stars for finding Li-rich K giants, and the method used for identifying Li-rich candidates using low-resolution spectra. The sample has 2000 giants within a mass range of 0.8 to $3.0\textit{M}_{\odot }$. Sample stars were selected from the Hipparcos catalogue with colour (B–V) and luminosity $(\textit{L}/\textit{L}_{\odot }$) in such way that the sample covers RGB evolution from its base towards RGB tip passing through first dredge-up and luminosity bump. Low-resolution (R $\approx$ 2000, 3500, 5000) spectra were obtained for all sample stars. Using core strength ratios of lines at Li I 6707 Å and its adjacent line Ca I 6717 Å  we successfully identified 15 K giants with A(Li) > 1.5 dex, which are defined as Li-rich K giants. The results demonstrate the usefulness of low-resolution spectra to measure Li abundance and identify Li-rich giants from a large sample of stars in relatively shorter time periods.