Know the Star, Know the Planet. III. A Stellar Companion to the Host Star of the Eccentric Exoplanet HD 8673b

Creators: Roberts, Lewis C., Jr.; Riddle, Reed L.; Bui, Khanh; Croner, Ernest; Dekany, Richard G.; Hale, David; Henning, John; Kulkarni, Shrinivas; McKenna, Dan; Milburn, Jennifer; Tendulkar, Shriharsh P.; Zolkower, Jeff

Abstract

HD 8673 hosts a massive exoplanet in a highly eccentric orbit (e = 0.723). Based on two epochs of speckle interferometry a previous publication identified a candidate stellar companion. We observed HD 8673 multiple times with the 10 m Keck II telescope, the 5 m Hale telescope, the 3.63 m Advanced Electro-Optical System telescope, and the 1.5 m Palomar telescope in a variety of filters with the aim of confirming and characterizing the stellar companion. We did not detect the candidate companion, which we now conclude was a false detection, but we did detect a fainter companion. We collected astrometry and photometry of the companion on six epochs in a variety of filters. The measured differential photometry enabled us to determine that the companion is an early M dwarf with a mass estimate of 0.33–0.45 M_☉. The companion has a projected separation of 10 AU, which is one of the smallest projected separations of an exoplanet host binary system. Based on the limited astrometry collected, we are able to constrain the orbit of the stellar companion to a semimajor axis of 35–60 AU, an eccentricity ≤0.5, and an inclination of 75°–85°. The stellar companion has likely strongly influenced the orbit of the exoplanet and quite possibly explains its high eccentricity.

Additional Information

© 2015 American Astronomical Society. Received 2014 June 20; accepted 2015 February 25; published 2015 March 30. The research in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. This paper is based on observations from a number of observatories, including the Maui Space Surveillance System, operated by the US Air Force Research Laboratory's Directed Energy Directorate. Additional observations were made at the Hale Telescope, Palomar Observatory as part of a continuing collaboration between the California Institute of Technology, NASA/JPL, NOAO, Oxford University, Stony Brook University, and the National Astronomical Observatories of China. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The W.M. Keck Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The Robo-AO system is supported by collaborating partner institutions, the California Institute of Technology and the Inter-University Centre for Astronomy and Astrophysics, by the National Science Foundation under grant Nos. AST-0906060, AST-0960343, and AST-1207891, by a grant from the Mt. Cuba Astronomical Foundation and by a gift from Samuel Oschin. C.B. acknowledges support from the Alfred P. Sloan Foundation. This research made use of the Washington Double Star Catalog maintained at the U.S. Naval Observatory, the SIMBAD database, operated by the CDS in Strasbourg, France, NASA's Astrophysics Data System and data products from the 2MASS, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. Facilities: AEOS (Visible Imager), Hale (PHARO), Keck:II (NIRC2), PO:1.5 m (Robo-AO).

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