We report 78 secondary eclipse depths for a sample of 36 transiting hot Jupiters observed at 3.6- and 4.5 \mu m using the Spitzer Space Telescope .
Our eclipse results for 27 of these planets are new , and include highly irradiated worlds such as KELT-7b , WASP-87b , WASP-76b , and WASP-64b , and important targets for JWST such as WASP-62b .
We find that WASP-62b has a slightly eccentric orbit ( e \cos { \omega } = 0.00614 \pm { 0.00058 } ) , and we confirm the eccentricity of HAT-P-13b and WASP-14b .
The remainder are individually consistent with circular orbits , but we find statistical evidence for eccentricity increasing with orbital period in our range from 1 to 5 days .
Our day-side brightness temperatures for the planets yield information on albedo and heat redistribution , following \citet cowan .
Planets having maximum day side temperatures exceeding \sim 2200 K are consistent with zero albedo and distribution of stellar irradiance uniformly over the day-side hemisphere .
Our most intriguing result is that we detect a systematic difference between the emergent spectra of these hot Jupiters as compared to blackbodies .
The ratio of observed brightness temperatures , Tb ( 4.5 ) /Tb ( 3.6 ) , increases with equilibrium temperature by 98 \pm 26 parts-per-million per Kelvin , over the entire temperature range in our sample ( 800K to 2500K ) .
No existing model predicts this trend over such a large range of temperature .
We suggest that this may be due to a structural difference in the atmospheric temperature profile between the real planetary atmospheres as compared to models .