A Substellar Companion to the Intermediate-Mass Giant 11 Comae

• Published in: The Astrophysical journal 2008-01, Vol.672 (1), p.553-557
• Main Authors: Liu, Y.-J, Sato, Bun'ei, Zhao, G, Noguchi, Kunio, Wang, H, Kambe, Eiji, Ando, Hiroyasu, Izumiura, Hideyuki, Chen, Y.-Q, Okada, Norio, Toyota, Eri, Omiya, Masashi, Masuda, Seiji, Takeda, Yoichi, Murata, Daisuke, Itoh, Yoichi, Yoshida, Michitoshi, Kokubo, Eiichiro, Ida, Shigeru
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/523297

We report the detection of a substellar companion orbiting the intermediate-mass giant star 11 Com (G8 III). Precise Doppler measurements of the star from Xinglong Station and Okayama Astrophysical Observatory (OAO) reveal Keplerian velocity variations with an orbital period of 326.03 plus or minus 0.32 days, a semiamplitude of 302.8 plus or minus 2.6 m s super(-1) and an eccentricity of 0.231 plus or minus 0.005. Adopting a stellar mass of 2.7 plus or minus 0.3 M [unk], the minimum mass of the companion is 19.4 plus or minus 1.5 [unk], well above the deuterium-burning limit, and the semimajor axis is 1.29 plus or minus 0.05 AU. This is the first result from a joint planet-search program between China and Japan aimed at revealing the statistics of substellar companions around intermediate-mass giants. 11 Com b emerged from 300 targets of the planet-search program at OAO. The program's current detection rate of brown dwarf candidates seems to be comparable to the rate of such detections around solar-type stars with orbital separations of [unk]3 AU.