Comparative planetary atmospheres: Models of TrES-1 and HD 209458B

We present new self-consistent atmosphere models for the transiting planets TrES-1 and HD 209458b. The planets were recently observed with the Spitzer Space Telescope in bands centered on 4.5 and 8.0 μm, for TrES-1, and 24 μm, for HD 209458b. We find that standard solar-metallicity models fit the observations for HD 209458b. For TrES-1, which has a T_eff ∼ 300 K cooler, we find that models with a metallicity 3-5 times enhanced over solar abundances can match the 1 σ error bar at 4.5 μm and 2 σ at 8.0 μm. Models with solar abundances that include energy deposition into the stratosphere give fluxes that fall within the 2 σ error bars in both bands. The best-fit models for both planets assume that reradiation of absorbed stellar flux occurs over the entire planet. For all models of both planets, we predict planet-to-star flux ratios in other Spitzer bandpasses.