1107.5750 (Jean-Michel Désert et al.)

The hot-Jupiter Kepler-17b: discovery, obliquity from stroboscopic starspots, and atmospheric characterization    [PDF]

Jean-Michel Désert, David Charbonneau, Brice-Olivier Demory, Sarah Ballard, Joshua A. Carter, Jonathan J. Fortney, William D. Cochran, Michael Endl, Samuel N. Quinn, Howard T. Isaacson, Francois Fressin, Lars A. Buchhave, David W. Latham, Heather A. Knutson, Stephen T. Bryson, Guillermo Torres, Jason F. Rowe, Natalie M. Batalha, William J. Borucki, Timothy M. Brown, Douglas A. Caldwell, Jessie L. Christiansen, Drake Deming, Daniel C. Fabrycky, Eric B. Ford, Ronald L. Gilliland, Michaël Gillon, Michaël R. Haas, Jon M. Jenkins, Karen Kinemuchi, David Koch, Jack J. Lissauer, Fergal Mullally, Phillip J. MacQueen, Geoffrey W. Marcy, Dimitar D. Sasselov, Sara Seager, Martin Still, Peter Tenenbaum, Kamal Uddin, Joshua N. Winn

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 (HET) show a Doppler signal of 420+/-15 m.s-1. From a transit-based estimate of the host star's mean density, combined with an estimate of the stellar effective temperature T_eff=5630+/-100 K from high-resolution spectra, we infer a stellar host mass of 1.061+/-0.067 M_sun and a stellar radius of 1.019+/-0.033 R_jup. We estimate the planet mass and radius to be Mp=2.450+/-0.114 M_jup and Rp=1.312+/-0.018 R_jup and a planet density near 1.35 g.cm-3. 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, 8 times the 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 deg. 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<0.0011). The brightness temperatures of the planet the infrared bandpasses are T_3.6um=1880+/-100 K and T4.5um=1770+/-150 K. We measure the optical geometric albedo A_g in the Kepler bandpass and find A_g = 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.

View original: http://arxiv.org/abs/1107.5750