Thursday, August 1, 2013

1307.8128 (Roberto Sanchis-Ojeda et al.)

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

Roberto Sanchis-Ojeda, Joshua N. Winn, Geoffrey W. Marcy, Andrew W. Howard, Howard Isaacson, John Asher Johnson, Guillermo Torres, Simon Albrecht, Tiago L. Campante, William J. Chaplin, Guy R. Davies, Mikkel L. Lund, Joshua A. Carter, Rebekah I. Dawson, Lars A. Buchhave, Mark E. Everett, Debra A. Fischer, John C. Geary, Ronald L. Gilliland, Elliott P. Horch, Steve B. Howell, David W. Latham
We present the discovery and characterization of a giant planet orbiting the young Sun-like star Kepler-63 (KOI-63, $m_{\rm Kp} = 11.6$, $T_{\rm eff} = 5576$ K, $M_\star = 0.98\, M_\odot$). The planet transits every 9.43 days, with apparent depth variations and brightening anomalies caused by large starspots. The planet's radius is $6.1 \pm 0.2 R_{\earth}$, 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 we can place a rough upper bound of $120 M_{\earth}$ (3$\sigma$). The host star has a high obliquity ($\psi$ = $104^{\circ}$), 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.
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