The hot-Jupiter Kepler-17b : Discovery, obliquity from stroboscopic starspots, and atmospheric characterization
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Author
Désert, J.-M.
Charbonneau, D.
Ballard, S.
Carter, J.A.
Quinn, S.N.
Fressin, F.
Latham, D.W.
Torres, G.
Lissauer, J.J.
Sasselov, D.D.
Demory, B.-O.
Seager, S.
Winn, J.N.
Fortney, J.J.
Fabrycky, D.C.
Cochran, W.D.
Endl, M.
MacQueen, P.J.
Isaacson, H.T.
Knutson, H.A.
Marcy, G.W.
Buchhave, L.A.
Bryson, S.T.
Rowe, J.F.
Borucki, W.J.
Christiansen, J.L.
Haas, M.R.
Koch, D.
Batalha, N.M.
Brown, T.M.
Caldwell, D.A.
Jenkins, J.M.
Mullally, F.
Tenenbaum, P.
Deming, D.
Ford, E.B.
Gilliland, R.L.
Gillon, M.
Kinemuchi, K.
Still, M.
Lucas, P.W.
Uddin, K.
Attention
2299/7201
Abstract
This paper reports the discovery and characterization of the transiting hot giant exoplanet Kepler-17b. The planet has an orbital period of 1.486 days, and radial velocity measurements from the Hobby-Eberly Telescope show a Doppler signal of 419.5 m s. From a transit-based estimate of the host star's mean density, combined with an estimate of the stellar effective temperature T = 5630 ± 100 from high-resolution spectra, we infer a stellar host mass of 1.06 ± 0.07 M and a stellar radius of 1.02 ± 0.03R . We estimate the planet mass and radius to be M = 2.45 0.11 M and R = 1.31 ± 0.02R . The host star is active, with dark spots that are frequently occulted by the planet. The continuous monitoring of the star reveals a stellar rotation period of 11.89 days, eight times the planet's orbital period; this period ratio produces stroboscopic effects on the occulted starspots. The temporal pattern of these spot-crossing events shows that the planet's orbit is prograde and the star's obliquity is smaller than 15°. We detected planetary occultations of Kepler-17b with both the Kepler and Spitzer Space Telescopes. We use these observations to constrain the eccentricity, e, and find that it is consistent with a circular orbit (e < 0.011). The brightness temperatures of the planet's infrared bandpasses are = 1880 ± 100 K and = 1770 ± 150 K. We measure the optical geometric albedo A in the Kepler bandpass and find A = 0.10 ± 0.02. The observations are best described by atmospheric models for which most of the incident energy is re-radiated away from the day side.