On the Presence of Water and Global Circulation in the Transiting Planet HD 189733b

Detailed models are compared to recent infrared observations of the nearby extrasolar planet, HD 189733b. It is demonstrated that atmospheric water is present and that the planet's day side has a non-isothermal structure down to gas pressures of ~ 0.1 bars. Furthermore, model spectra with different amounts of CO are compared to the observations and an atmosphere absent of CO is excluded at roughly 2-sigma. Constraining the CO concentration beyond that is unfortunately not possible with the current Spitzer photometry. However, radically enhanced (or depleted) metal abundances are unlikely and the basic composition of this planet is probably similar to that of its host star. When combined with Spitzer observations, a recent ground-based upper limit for the K-band day side flux allows one to estimate the day-to-night energy redistribution efficiency to be ~ 43%.