Extrasolar Giant Planets under Strong Stellar Irradiation

Abstract

We investigate irradiation of extrasolar giant planets (EGPs) by treating the radiative transfer in detail, so that the flux from the parent star interacts with all relevant depths of the planetary atmosphere with no need for a preassumed albedo. Rayleigh scattering (in dust-free models) increases the EGP's flux by orders of magnitude shortward of the Ca II H and K doublet (3930 Å), and the spectral features of the parent star are exactly reflected. The inclusion of dust increases the reflected flux in the blue. In the optical and near-IR, the thermal absorption of the planet takes over, but the absorption features are changed by the irradiation.