High Lithium Abundance Connection with the Chromospheric Helium in Red Giants: Spectroscopic and Asteroseismic analyses

We present a study of correlations between high Li abundances and strong chromospheric He I 10830 \AA\ absorption line strengths in Kepler field giant stars.

Our sample includes 84 giants with detectable solar-like oscillations in their lightcurves, and their Li abundances come from the literature or were measured here using LAMOST medium-resolution spectra.

Evolutionary phases are determined through asteroseismic analysis, with mixed-mode period spacing (\Delta P) used to infer the time evolution of RC giants.

Near-infrared observations of the He I \lambda 10830 line were obtained with the high-resolution Habitable-zone Planet Finder (HPF) spectrograph on the Hobby-Eberly Telescope (HET).

We find high Li abundances and strong He I lines exclusively among red clump (RC) giants, with their absence in red giant branch stars suggesting a shared origin linked to the He-flash.

Additionally, a steady decline in He I strength with decreasing Li abundance among RC giants indicates a correlation between these properties.

Older, Li-normal RC giants are He-weak, while most younger super-Li-rich giants are He-strong, suggesting temporal evolution of both phenomena.

We hypothesize that the core He-flash and subsequent sub-flashes may enhance Li abundances in RC giant photospheres and trigger heightened chromospheric activity, leading to stronger He I \lambda 10830 \AA\ lines in younger RCs.

Over time, post-He-flash, chromospheric activity diminishes, resulting in weaker He I lines in older, Li-normal RCs.

;Comment: 17 pages, 11 figures, 1 table, Accepted for publication in ApJ