A Substellar Companion in a 1.3 yr Nearly Circular Orbit of HD 16760

Creators: Sato, Bun'ei; Fischer, Debra A.; Ida, Shigeru; Harakawa, Hiroki; Omiya, Masashi; Johnson, John A.; Marcy, Geoffrey W.; Toyota, Eri; Hori, Yasunori; Isaacson, Howard; Howard, Andrew W.; Peek, Kathryn M. G.

Abstract

We report the detection of a substellar companion orbiting the G5 dwarf HD 16760 from the N2K sample. Precise Doppler measurements of the star from Subaru and Keck revealed a Keplerian velocity variation with a period of 466.47 ± 0.35 d, a semiamplitude of 407.71 ± 0.84 m s^(–1), and an eccentricity of 0.084 ± 0.003. Adopting a stellar mass of 0.78 ± 0.05 M_☉, we obtain a minimum mass for the companion of 13.13 ± 0.56 M_(JUP), which is close to the planet/brown-dwarf transition, and the semimajor axis of 1.084 ± 0.023 AU. The nearly circular orbit despite the large mass and intermediate orbital period makes this companion unique among known substellar companions.

Additional Information

© 2009 American Astronomical Society. Received 2009 March 2; accepted 2009 July 31; published 2009 August 31. Based on data collected by the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. Based on observations obtained at the W. M. Keck Observatory, which is operated by the University of California and the California Institute of Technology. Keck time has been granted by NOAO and NASA. We thank Akito Tajitsu and Tae-Soo Pyo for their expertise and support of the Subaru HDS observations. We gratefully acknowledge the dedication and support of the Keck Observatory staff, in particular Grant Hill for support with HIRES. B.S. is supported by MEXT's program "Promotion of Environmental Improvement for Independence of Young Researchers" under the Special Coordination Funds for Promoting Science and Technology. DF gratefully acknowledges support from NASA grant NNG05G164G. This research has made use of the Simbad database, operated at CDS, Strasbourg, France. The authors extend thanks to those of native Hawaiian ancestry on whose sacred mountain of Mauna Kea we are privileged to be guests. Without their generous hospitality, the Subaru and Keck observations presented herein would not have been possible.

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