We present new warm Spitzer occultation photometry of WASP-26 at 3.6 \micron and 4.5 \micron along with new transit photometry taken in the g , r and i bands .
We report the first detection of the occultation of WASP-26b , with occultation depths at 3.6 \mu m and 4.5 \mu m of 0.00126 \pm 0.00013 and 0.00149 \pm 0.00016 corresponding to brightness temperatures of 1825 \pm 80 K and 1725 \pm 89 K , respectively .
We find that the eccentricity of the orbit is consistent with a circular orbit at the 1 \sigma level ( e = 0.0028 ^ { +0.0097 } _ { -0.0022 } , 3 \sigma upper limit e < 0.04 ) .
According to the activity-inversion relation of , WASP-26b is predicted to host a thermal inversion .
The brightness temperatures deduced from the eclipse depths are consistent with an isothermal atmosphere , although it is within the uncertainties that the planet may host a weak thermal inversion .
The data are equally well fit by atmospheric models with or without a thermal inversion .
We find that variation in activity of solar-like stars does not change enough over the time-scales of months or years to change the interpretation of the activity-inversion relation , provided that the measured activity level is averaged over several nights .
Further data are required to fully constrain the thermal structure of the atmosphere because the planet lies very close to the boundary between atmospheres with and without a thermal inversion .