Kepler-63b: A Giant Planet in a Polar Orbit around a Young Sun-like Star

Creators: Sanchis-Ojeda, Roberto; Winn, Joshua N.; Marcy, Geoffrey W.; Howard, Andrew W.; Isaacson, Howard T.; Johnson, John Asher; Torres, Guillermo; Albrecht, Simon; Campante, Tiago L.; Chaplin, William J.; Davies, Guy R.; Lund, Mikkel N.; Carter, Joshua A.; Dawson, Rebekah I.; Buchhave, Lars A.; Everett, Mark E.; Fischer, Debra A.; Geary, John C.; Gilliland, Ronald L.; Horch, Elliott P.; Howell, Steve B.; Latham, David W.

Abstract

We present the discovery and characterization of a giant planet orbiting the young Sun-like star Kepler-63 (KOI-63, m_(Kp) = 11.6, T_(eff) = 5576 K, M_★ = 0.98 M_☉). The planet transits every 9.43 days, with apparent depth variations and brightening anomalies caused by large starspots. The planet's radius is 6.1 ± 0.2 R_⊕, based on the transit light curve and the estimated stellar parameters. The planet's mass could not be measured with the existing radial-velocity data, due to the high level of stellar activity, but if we assume a circular orbit, then we can place a rough upper bound of 120 M_⊕ (3σ). The host star has a high obliquity (ψ = 104°), based on the Rossiter-McLaughlin effect and an analysis of starspot-crossing events. This result is valuable because almost all previous obliquity measurements are for stars with more massive planets and shorter-period orbits. In addition, the polar orbit of the planet combined with an analysis of spot-crossing events reveals a large and persistent polar starspot. Such spots have previously been inferred using Doppler tomography, and predicted in simulations of magnetic activity of young Sun-like stars.

Additional Information

© 2013 American Astronomical Society. Received 2013 March 23; accepted 2013 August 4; published 2013 September 4. We thank the anonymous referee for numerous insightful suggestions that led to major improvements in this paper. We also thank Andrew Collier Cameron, Bryce Croll, and Benjamin Brown for helpful discussions, and the entire Kepler team for the success of the mission. R.S.O. and J.N.W. acknowledge NASA support through the Kepler Participating Scientist program. Kepler was competitively selected as the tenth Discovery mission. Funding for this mission was provided by NASA's Science Mission Directorate. The data presented in this article were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. J.A.C. acknowledges support by NASA through a Hubble Fellowship (grant HF-51267.01-A). R.I.D. is supported by the NSF-GRFP (DGE-1144152). J.A.J. is supported by generous grants from the Alfred P. Sloan Foundation and the David and Lucile Packard Foundation. T.L.C., W.J.C., and G.R.D. acknowledge the support of the UK Science and Technology Facilities Council (STFC). Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (grant agreement DNRF106). This research was partly supported by the ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) funded by the European Research Council (grant agreement No. 267864). G.T. acknowledges partial support for this work from NSF grant AST-1007992.

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