2025ApJ...980..265M -
Astrophys. J., 980, 265 (2025/February-3)
High Lithium Abundance Connection with the Chromospheric Helium in Red Giants: Spectroscopic and Asteroseismic Analyses.
MALLICK A., SNEDEN C., REDDY B.E. and AFSAR M.
Abstract (from CDS):
We present a study of correlations between high Li abundances and strong chromospheric He Iλ10830 absorption-line strengths in Kepler field giant stars. Our sample includes 84 giants with detectable solar-like oscillations in their light curves, and their Li abundances come from the literature or are measured here using LAMOST medium-resolution spectra. Evolutionary phases are determined through asteroseismic analysis, with mixed-mode period spacing (ΔP) used to infer the time evolution of red clump (RC) giants. Near-IR observations of the He Iλ10830 line were obtained with the high-resolution Habitable-zone Planet Finder spectrograph on the Hobby-Eberly Telescope. We find high Li abundances and strong He I lines exclusively among 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 subflashes may enhance Li abundances in RC giant photospheres and trigger heightened chromospheric activity, leading to stronger He Iλ10830 lines in younger RCs. Over time, following He flash, chromospheric activity diminishes, resulting in weaker He I lines in older, Li-normal RCs.
Abstract Copyright:
© 2025. The Author(s). Published by the American Astronomical Society.
Journal keyword(s):
Red giant clump - Stellar oscillations - Stellar abundances - Stellar chromospheres - Helium burning
Simbad objects:
84
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