Planets around the evolved stars 24 Boötis and γ Libra: A 30 d-period planet and a double giant-planet system in possible 7:3 MMR

PASJ: Publications of the Astronomical Society of Japan

Sato, Bun’ei¹  Takarada, Takuya¹  Nagasawa, Makiko²  Ando, Hiroyasu³  Ida, Shigeru⁴  Harakawa, Hiroki⁴  Yoshida, Michitoshi⁴  Omiya, Masashi⁴  Kokubo, Eiichiro⁵  Takeda, Yoichi⁶  Izumiura, Hideyuki⁶  Kambe, Eiji⁷  Itoh, Yoichi⁷ 

[1] Department of Earth and Planetary Sciences, School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan;Department of Physics, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan;Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan;National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan;Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, 407-2, Nishigaichi, Sayo, Hyogo 679-5313, Japan;Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Kamogata, Okayama 719-0232, Japan;The Graduate University for Advanced Studies, Shonan Village, Hayama, Kanagawa 240-0193, Japan

关键词: techniques: radial velocities;    stars: individual;    (stars:) planetary systems;   

DOI  :  10.1093/pasj/psy052

学科分类：天文学(综合)

来源: Oxford University Press

【 摘 要 】

We report the detection of planets around two evolved giant stars from radial velocity measurements at Okayama Astrophysical observatory. 24 Boo (G3 IV) has a mass of |$0.99\,M_{\odot }$|⁠, a radius of |$10.64\,R_{\odot }$|⁠, and a metallicity of [Fe/H] = −0.77. The star hosts one planet with a minimum mass of 0.91 MJup and an orbital period of 30.35 d. The planet has one of the shortest orbital periods among those ever found around evolved stars using radial-velocity methods. The stellar radial velocities show additional periodicity with 150 d, which can probably be attributed to stellar activity. The star is one of the lowest-metallicity stars orbited by planets currently known. γ Lib (K0 III) is also a metal-poor giant with a mass of |$1.47\,M_{\odot }$|⁠, a radius of |$11.1\,R_{\odot }$|⁠, and [Fe/H] = −0.30. The star hosts two planets with minimum masses of 1.02 MJup and 4.58 MJup, and periods of 415 d and 964 d, respectively. The star has the second-lowest metallicity among the giant stars hosting more than two planets. Dynamical stability analysis for the γ Lib system sets the minimum orbital inclination angle to be about 70° and suggests that the planets are in 7:3 mean-motion resonance, though the current best-fitting orbits for the radial-velocity data are not totally regular.

【 授权许可】

CC BY