Abstract:
In this work, we studied the distribution of lithium abundances in giants as a function of stellar mass. We used a
sample of 1240 giants common among Kepler photometric and LAMOST medium-resolution (R ≈ 7500)
spectroscopic survey fields. The asteroseismic ΔP–Δν diagram is used to define core He-burning red clump giants
and red giant branch stars with an inert He core. Li abundances have been derived using spectral synthesis for all
sample stars. Directly measured values of asteroseismic parameters ΔP (or ΔΠ1) and Δν are either taken from the
literature or measured in this study. Of the 777 identified red clump giants, we found 668 low-mass ( 2 Me)
primary red clump giants and 109 high-mass (>2 Me) secondary red clump giants. Observed Li abundances in
secondary red clump giants agree with the theoretical model predictions. The lack of Li-rich giants among
secondary red clump giants and the presence of Li-rich, including super Li-rich, giants among primary red clump
stars reinforces the idea that helium flash holds the key for Li enrichment among low-mass giants. The results will
further constrain theoretical models searching for a physical mechanism for Li enhancement among low-mass red
clump giants. Results also serve as observational evidence that only giants with mass less than ≈2 Me develop a
degenerate He core and undergo He flash.
