HAT-P-56b: An Inflated Massive Hot Jupiter Transiting a Bright F Star Followed Up with K2 Campaign 0 Observations

We report the discovery of HAT-P-56b by the HATNet survey, an inflated hot Jupiter transiting a bright F-type star in Field 0 of NASA's K2 mission. We combine ground-based discovery and follow-up light curves with high precision photometry from K2, as well as ground-based radial velocities from the Tillinghast Reflector Echelle Spectrograph on the Fred Lawrence Whipple Observatory 1.5 m telescope to determine the physical properties of this system. HAT-P-56b has a mass of 2.18 {M}_{{J}}, radius of 1.47 {R}_{{J}}, and transits its host star on a near-grazing orbit with a period of 2.7908 day. The radius of HAT-P-56b is among the largest known for a planet with {M}_p\gt 2 {M}_{{J}}. The host star has a V-band magnitude of 10.9, mass of 1.30 {M}_⊙ , and radius of 1.43 {R}_⊙ . The periodogram of the K2 light curve suggests that the star is a γ Dor variable. HAT-P-56b is an example of a ground-based discovery of a transiting planet, where space-based observations greatly improve the confidence in the confirmation of its planetary nature, and also improve the accuracy of the planetary parameters.

Based on observations obtained with the Hungarian-made Automated Telescope Network. Based in part on observations obtained with the Tillinghast Reflector 1.5 m telescope and the 1.2 m telescope, both operated by the Smithsonian Astrophysical Observatory at the Fred Lawrence Whipple Observatory in Arizona. Based in part on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium. Based in part on observations obtained with the Kepler Space Craft in the K2 Campaign 0 Mission.