A High-eccentricity Component in the Double-planet System around HD 163607 and a Planet around HD 164509

Creators: Giguere, Matthew J.; Fischer, Debra A.; Howard, Andrew W.; Johnson, John A.; Henry, Gregory W.; Wright, Jason T.; Marcy, Geoffrey W.; Isaacson, Howard T.; Hou, Fengii; Spronck, Julien

Abstract

We report the detection of three new exoplanets from Keck Observatory. HD 163607 is a metal-rich G5IV star with two planets. The inner planet has an observed orbital period of 75.29 ± 0.02 days, a semi-amplitude of 51.1 ± 1.4 m s^(–1), an eccentricity of 0.73 ± 0.02, and a derived minimum mass of MP sin i = 0.77 ± 0.02 M_(Jup). This is the largest eccentricity of any known planet in a multi-planet system. The argument of periastron passage is 78.7 ± 2°0; consequently, the planet's closest approach to its parent star is very near the line of sight, leading to a relatively high transit probability of 8%. The outer planet has an orbital period of 3.60 ± 0.02 years, an orbital eccentricity of 0.12 ± 0.06, and a semi-amplitude of 40.4 ± 1.3 m s^(–1). The minimum mass is MP sin i = 2.29 ± 0.16 M _(Jup). HD 164509 is a metal-rich G5V star with a planet in an orbital period of 282.4 ± 3.8 days and an eccentricity of 0.26 ± 0.14. The semi-amplitude of 14.2 ± 2.7 m s^(–1) implies a minimum mass of 0.48 ± 0.09 M_(Jup). The radial velocities (RVs) of HD 164509 also exhibit a residual linear trend of –5.1 ± 0.7 m s–1 year–1, indicating the presence of an additional longer period companion in the system. Photometric observations demonstrate that HD 163607 and HD 164509 are constant in brightness to submillimagnitude levels on their RV periods. This provides strong support for planetary reflex motion as the cause of the RV variations.

Additional Information

© 2012 The American Astronomical Society. Received 2010 December 17; accepted 2011 September 9; published 2011 December 7. 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 gratefully acknowledge the dedication and support of the Keck Observatory staff, in particular Grant Hill and Scott Dahm for their support with HIRES and Greg Wirth and Bob Kibrick for supporting remote observing. We thank the NASA Telescope assignment committees for generous allocations of telescope time. We thank the anonymous referee for useful comments and suggestions. Fischer acknowledges support from NASA Grant NNX08AF42G and NASA Keck PI data analysis funds. G.W.H. acknowledges support from NASA, NSF, Tennessee State University, and the State of Tennessee through its Centers of Excellence program. J.T.W. gratefully acknowledges the Center for Exoplanets and Habitable Worlds, supported by the Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. 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 Keck observations presented herein would not have been possible.

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