Theoretical Spectra and Atmospheres of Extrasolar Giant Planets

We present a comprehensive theory of the spectra and atmospheres ofirradiated extrasolar giant planets. We explore the dependences on stellartype, orbital distance, cloud characteristics, planet mass, and surfacegravity. Phase-averaged spectra for specific known extrasolar giant planetsthat span a wide range of the relevant parameters are calculated, plotted, anddiscussed. The connection between atmospheric composition and emergent spectrumis explored in detail. Furthermore, we calculate the effect of stellarinsolation on brown dwarfs. We review a variety of representative observationaltechniques and programs for their potential for direct detection, in light ofour theoretical expectations, and we calculate planet-to-star flux ratios as afunction of wavelength. Our results suggest which spectral features are mostdiagnostic of giant planet atmospheres and reveal the best bands in which toimage planets of whatever physical or orbital characteristics.Comment: 47 pages, plus 36 postscript figures; with minor revisions, accepted to the Astrophysical Journal, May 10, 2003 issu