"Atmospheric characterization of the hot Jupiter exoplanet Kepler-13Ab"

One of the expanding fields of exoplanet study is the detailed characterization of exoplanets, including the properties of their atmospheres. This is currently being done for a growing sample of the so-called hot Jupiters - gas-giant planets orbiting close-in to their host star - a class of planets that does not exist in the Solar System. I will present the results of our atmospheric study of Kepler-13Ab, which is a unique transiting exoplanet. It is one of very few known short-period (1.76 day) planets orbiting a bright (V = 9.95 mag), hot, A-type star. Therefore, it is among the hottest planets currently known. We have observed the planet’s occultation (secondary eclipse; when the planet moves behind the host star) using data from the optical to the IR, obtained with the Kepler and Spitzer space telescopes along with a ground-based observation in the near-IR. For the planetary hemisphere facing the star we derive a temperature of 2,750 +/- 160 K as the effective temperature of a black body that will show the same occultation depths, and find evidence for an unusually high geometric albedo, measured to be Ag = 0.33+0.04-0.06. In addition, we identify the presence of atmospheric inversion, where the temperature increases with decreasing pressure. Using the Kepler full orbital phase light curve we revise the planet’s mass to Mp = 4.94 - 8.09 Jupiter mass based on the amplitudes of the beaming effect and ellipsoidal distortion. We also obtain a revised stellar radius that combined with the previously measured planet to star radii ratio gives a revised planet radius of Rp = 1.406 +/- 0.038 Jupiter radius. Finally, we note that the Kepler mid-occultation time measured here is 34.2 +/- 6.9 s earlier than expected based on the expected time delay due to light travel time, and discuss possible causes.

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