Published online by Cambridge University Press: 01 May 2008
We present here results from observations of TrES-2 made using the Infrared Array Camera on the Spitzer Space Telescope. We monitored this transiting system during two secondary eclipses, when the planetary emission is blocked by the star. The resulting decrease in flux is 0.135 ± 0.036%, 0.245 ± 0.027%, 0.162 ± 0.064%, and 0.295 ± 0.066%, at 3.6-μm, 4.5-μm, 5.8-μm, and 8.0-μm, respectively. We find evidence for a temperature inversion in the atmosphere of TrES-2, which is predicted by Fortney and collaborators based on the proposed importance of TiO and VO opacities for this highly irradiated gas giant. We also find the time of the center of the eclipse to be consistent with predictions from transit timing observations of TrES-2. This implies that TrES-2 most likely has a circular orbit, and thus does not obtain additional thermal energy from tidal dissipation of a non-zero orbital eccentricity, a proposed explanation of the large planetary radius.