摘要：Aims.Previous secondary eclipse observations of the hot Jupiter Qatar-1b in theKs band suggest that it may have an unusually high day side temperature, indicative of minimal heat redistribution. There have also been indications that the orbit may be slightly eccentric, possibly forced by another planet in the system. We investigate the day side temperature and orbital eccentricity using secondary eclipse observations withSpitzer.Methods.We observed the secondary eclipse withSpitzer/IRAC in subarray mode, in both 3.6 and 4.5μm wavelengths. We used pixel-level decorrelation to correct forSpitzer’s intra-pixel sensitivity variations and thereby obtain accurate eclipse depths and central phases.Results.Our 3.6μm eclipse depth is 0.149 ± 0.051% and the 4.5μm depth is 0.273 ± 0.049%. Fitting a blackbody planet to our data and two recentKs band eclipse depths indicates a brightness temperature of 1506 ± 71 K. Comparison to model atmospheres for the planet indicates that its degree of longitudinal heat redistribution is intermediate between fully uniform and day-side only. The day side temperature of the planet is unlikely to be as high (1885 K) as indicated by the ground-based eclipses in theKs band, unless the planet’s emergent spectrum deviates strongly from model atmosphere predictions. The average central phase for ourSpitzereclipses is 0.4984 ± 0.0017, yieldinge cos ω = −0.0028 ± 0.0027. Our results are consistent with a circular orbit, and we constrain e cos ωmuch more strongly than has been possible with previous observations.
