  We present here the results of our observations of TrES-2 using the Infrared
Array Camera on Spitzer. We monitored this transiting system during two
secondary eclipses, when the planetary emission is blocked by the star. The
resulting decrease in flux is 0.127%+-0.021%, 0.230%+-0.024%, 0.199%+-0.054%,
and 0.359%+-0.060%, at 3.6 microns, 4.5 microns, 5.8 microns, and 8.0 microns,
respectively. We show that three of these flux contrasts are well fit by a
black body spectrum with T_{eff}=1500 K, as well as by a more detailed model
spectrum of a planetary atmosphere. The observed planet-to-star flux ratios in
all four IRAC channels can be explained by models with and without a thermal
inversion in the atmosphere of TrES-2, although with different atmospheric
chemistry. Based on the assumption of thermochemical equilibrium, the chemical
composition of the inversion model seems more plausible, making it a more
favorable scenario. TrES-2 also falls in the category of highly irradiated
planets which have been theoretically predicted to exhibit thermal inversions.
However, more observations at infrared and visible wavelengths would be needed
to confirm a thermal inversion in this system. Furthermore, we find that the
times of the secondary eclipses are consistent with previously published times
of transit and the expectation from a circular orbit. 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 for the large radius of this planet.
