We present near-infrared Ks-band photometry bracketing the secondary eclipse of the hot Jupiter TrES-2b using the Wide-field Infrared Camera on the Canada-France-Hawaii Telescope .
We detect its thermal emission with an eclipse depth of 0.062 ^ { +0.013 } _ { -0.011 } % ( 5 \sigma ) .
Our best-fit secondary eclipse is consistent with a circular orbit ( a 3 \sigma upper limit on the eccentricity , e , and argument or periastron , \omega , of | e \cos \omega | < 0.0090 ) , in agreement with mid-infrared detections of the secondary eclipse of this planet .
A secondary eclipse of this depth corresponds to a day-side Ks-band brightness temperature of T _ { B } = 1636 ^ { +79 } _ { -88 } K .
Our thermal emission measurement when combined with the thermal emission measurements using Spitzer/IRAC from O ’ Donovan and collaborators suggest that this planet exhibits relatively efficient day to night-side redistribution of heat and a near isothermal dayside atmospheric temperature structure , with a spectrum that is well approximated by a blackbody .
It is unclear if the atmosphere of TrES-2b requires a temperature inversion ; if it does it is likely due to chemical species other than TiO/VO as the atmosphere of TrES-2b is too cool to allow TiO/VO to remain in gaseous form .
Our secondary eclipse has the smallest depth of any detected from the ground at around 2 \mu m to date .