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• Sanchis-Ojeda, Roberto
;
• Winn, Joshua N.
;
• Marcy, Geoffrey W.
;
• Howard, Andrew W.
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• Isaacson, Howard
;
• Johnson, John Asher
;
• Torres, Guillermo
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• Albrecht, Simon
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• Campante, Tiago L.
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• Chaplin, William J.
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• Davies, Guy R.
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• Lund, Mikkel N.
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• Carter, Joshua A.
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• Dawson, Rebekah I.
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• Buchhave, Lars A.
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• Everett, Mark E.
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• Fischer, Debra A.
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• Geary, John C.
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• 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_sstarf = 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.

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