Astronomy & Astrophysics Seminar: Atmospheric characterization of the hot Jupiter exoplanet Kepler-13Ab

Abstract:

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 the unique transiting exoplanet Kepler-13Ab. It is one of only two known short-period (1.76 day) planets orbiting a bright (V = 9.95 mag), hot A-type star (Teff = 7,650 K). We have observed the planetג€™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 K, comparable to the smallest main-sequence stars. We find evidence for a high geometric albedo, of about 0.3, which is unusually high for gas-giant planets, and identify the presence of atmospheric inversion, where the temperature increases with decreasing pressure. In addition, our revised planetary radius (1.4 Jupiter radius) is significantly smaller than previously thought, and our revised planetary mass, from measuring the beaming effect and ellipsoidal distortion in the Kepler phase curve, is 5 - 8 Jupiter mass. Therefore, this planet is a massive high-density hot Jupiter, with radius similar to those of other hot Jupiters. Finally, we find that the difference between the Kepler occultation time and transit time is half a minute shorter than expected from the light travel time delay, and discuss possible causes.

Seminar Organiser: Prof. Rennan Barkana