The Active Chromospheres of Lithium-rich Red Giant Stars*
Makaleler > Tam Makale · 2022
Yazarlar: Christopher Sneden, Melike AFŞAR, Zeynep BOZKURT, Monika Adamow, Anohita Mallick, Bacham E. Reddy, Steven Janowiecki, Suvrath Mahadevan, Brendan P. Bowler, Keith Hawkins, Karin Lind, Andrea K. Dupree, Joe P. Ninan, Neel Nagarajan, Gamze Bocek Topcu, Cynthia S. Froning, Chad F. Bender, Ryan Terrien, Lawrence W. Ramsey, Gregory N. Mace
ASTROPHYSICAL JOURNAL, SCI İndekslerine Giren Dergi, Uluslararası, Wos, 2022, cilt 940, ss 12-32
Özet
We have gathered near-infrared zyJ-band high-resolution spectra of nearly 300 field red giant stars with known lithium abundances in order to survey their He i lambda 10830 absorption strengths. This transition is an indicator of chromospheric activity and/or mass loss in red giants. The majority of stars in our sample reside in the red clump or red horizontal branch based on their V - J, M ( V ) color-magnitude diagram, and Gaia T (eff) and log(g) values. Most of our target stars are Li-poor in the sense of having normally low Li abundances, defined here as log epsilon(Li) < 1.25. Over 90% of these Li-poor stars have weak lambda 10830 features. However, more than half of the 83 Li-rich stars (log epsilon(Li) > 1.25) have strong lambda 10830 absorptions. These large lambda 10830 lines signal excess chromospheric activity in Li-rich stars; there is almost no indication of significant mass loss. The Li-rich giants may also have a higher binary fraction than Li-poor stars, based on their astrometric data. It appears likely that both residence on the horizontal branch and present or past binary interaction play roles in the significant Li-He connection established in this survey.