@article{2433a3dbbb8f4bfd8590370d10c75dcd,
title = "The Active Chromospheres of Lithium-rich Red Giant Stars",
abstract = "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 λ10830 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 ϵ(Li) < 1.25. Over 90\% of these Li-poor stars have weak λ10830 features. However, more than half of the 83 Li-rich stars (log ϵ(Li) > 1.25) have strong λ10830 absorptions. These large λ10830 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.",
author = "Christopher Sneden and Melike Af{\c s}ar and Zeynep Bozkurt and Monika Adam{\'o}w and Anohita Mallick and Reddy, \{Bacham E.\} and Steven Janowiecki and Suvrath Mahadevan and Bowler, \{Brendan P.\} and Keith Hawkins and Karin Lind and Dupree, \{Andrea K.\} and Ninan, \{Joe P.\} and Neel Nagarajan and Topcu, \{Gamze B{\"o}cek\} and Froning, \{Cynthia S.\} and Bender, \{Chad F.\} and Ryan Terrien and Ramsey, \{Lawrence W.\} and Mace, \{Gregory N.\}",
note = "We thank Claudia Aguilere-G{\'o}mez, Bengt Gustafsson, Noriyuki Matsunaga, George Preston, and our referee for helpful comments on this work. These results are based on observations obtained with the Habitable-zone Planet Finder Spectrograph on the Hobby–Eberly Telescope. We thank the Telescope Operators at the HET for the skillful execution of our observations with HPF. The Hobby–Eberly Telescope is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximilians-Universit{\"a}t M{\"u}nchen, and Georg-August Universit{\"a}t Gottingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly. The HET collaboration acknowledges the support and resources from the Texas Advanced Computing Center. We are happy to acknowledge support from NSF grants AST-1616040 (CS), AST-1908892 (GNM), and Technological Research Council of Turkey (T{\"U}BITAK), project No. 112T929 (MA). We thank Claudia Aguilere-G{\'o}mez, Bengt Gustafsson, Noriyuki Matsunaga, George Preston, and our referee for helpful comments on this work. These results are based on observations obtained with the Habitable-zone Planet Finder Spectrograph on the Hobby-Eberly Telescope. We thank the Telescope Operators at the HET for the skillful execution of our observations with HPF. The Hobby-Eberly Telescope is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximilians-Universit{\"a}t M{\"u}nchen, and Georg-August Universit{\"a}t Gottingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly. The HET collaboration acknowledges the support and resources from the Texas Advanced Computing Center. We are happy to acknowledge support from NSF grants AST-1616040 (CS), AST-1908892 (GNM), and Technological Research Council of Turkey (T{\"U}BITAK), project No. 112T929 (MA).",
year = "2022",
month = nov,
day = "1",
doi = "10.3847/1538-4357/ac922e",
language = "English (US)",
volume = "940",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "American Astronomical Society",
number = "1",
}