The Orbit and Mass of the Third Planet in the Kepler-56 System

Creators: Otor, Oderah Justin; Montet, Benjamin T.; Johnson, John Asher; Charbonneau, David; Collier-Cameron, Andrew; Howard, Andrew W.; Isaacson, Howard; Latham, David W.; López-Morales, Mercedes; Lovis, Christophe; Mayor, Michel; Micela, Giusi; Molinari, Emilio; Pepe, Francesco; Piotto, Giampaolo; Phillips, David F.; Queloz, Didier; Rice, Ken; Sasselov, Dimitar; Ségransan, Damien; Sozzetti, Alessandro; Udry, Stéphane; Watson, Chris

Abstract

While the vast majority of multiple-planet systems have orbital angular momentum axes that align with the spin axis of their host star, Kepler-56 is an exception: its two transiting planets are coplanar yet misaligned by at least 40° with respect to the rotation axis of their host star. Additional follow-up observations of Kepler-56 suggest the presence of a massive, non-transiting companion that may help explain this misalignment. We model the transit data along with Keck/HIRES and HARPS-N radial velocity data to update the masses of the two transiting planets and infer the physical properties of the third, non-transiting planet. We employ a Markov Chain Monte Carlo sampler to calculate the best-fitting orbital parameters and their uncertainties for each planet. We find the outer planet has a period of 1002 ± 5 days and minimum mass of 5.61 ± 0.38 M_(Jup). We also place a 95% upper limit of 0.80 m s^(−1) yr^(−1) on long-term trends caused by additional, more distant companions.

Additional Information

© 2016 The American Astronomical Society. Received 2016 August 10; revised 2016 September 17; accepted 2016 September 21; published 2016 November 15. We thank Eric Agol, Daniel Fabrycky, and Daniel Huber for comments and conversations which improved the quality of this manuscript. O.J.O. thanks the members and friends of the Banneker Institute, who made the summer in which this project began a fruitful time. He also thanks Neta Bahcall for allowing him to continue this research as his senior thesis. He gratefully acknowledges support from the Banneker Institute and Princeton's astrophysics department, Class of 1984, and Office of the Dean of Undergraduate Students in facilitating travel to AAS 227 to present this research. He would be remiss to forget the other members of the Party of Three and their associates. B.T.M. is supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE1144469. J.A.J. is supported by generous grants from the David and Lucile Packard Foundation and the Alfred P. Sloan Foundation. C.A.W. acknowledges support from STFC grant ST/L000709/1. This publication was made possible through the support of a grant from the John Templeton Foundation. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. This material is based upon work supported by the National Aeronautics and Space Administration under grant No. NNX15AC90G issued through the Exoplanets Research Program. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under Grant Agreement No. 313014 (ETAEARTH). 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 Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. The HARPS-N project was funded by the Prodex program of the Swiss Space Office (SSO), the Harvard University Origin of Life Initiative (HUOLI), the Scottish Universities Physics Alliance (SUPA), the University of Geneva, the Smithsonian Astrophysical Observatory (SAO), and the Italian National Astrophysical Institute (INAF), University of St. Andrews, Queens University Belfast, and University of Edinburgh. Facilities: Keck:I (HIRES) - , TNG (HARPS-N). -

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