Model bond albedos of extrasolar giant planets

The atmospheres of extrasolar giant planets are modeled with various effect ive temperatures and gravities, with and without clouds. Bond albedos are c omputed by calculating the ratio of the flux reflected by a planet (integra ted over wavelength) to the total stellar flux incident on the planet. This quantity is useful for estimating the effective temperature and evolution of a planet. We find it is sensitive to the stellar type of the primary. Fo r a 5 M-Jup planet the Bond albedo varies from 0.4 to 0.3 to 0.06 as the pr imary star varies from A5V to G2V to M2V in spectral type. It is relatively insensitive to the effective temperature and gravity for cloud-free planet s. Water clouds increase the reflectivity of the planet in the red, which i ncreases the Bond albedo. The Bond albedo increases by an order of magnitud e for a 13 M-Jup planet with an M2V primary when eater clouds are present. Silicate clouds, on the other hand, can either increase or decrease the Bon d albedo, depending on whether there are many small grains (the former) or few large grains (the latter). (C) 1999 Elsevier Science Ltd. All rights re served.