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We observe two secondary eclipses of the strongly irradiated transitingplanet WASP-33b in the Ks band, and one secondary eclipse each at 3.6- and 4.5microns using Warm Spitzer. This planet orbits an A5V delta-Scuti star that isknown to exhibit low amplitude non-radial p-mode oscillations at about0.1-percent semi-amplitude. We detect stellar oscillations in all of ourinfrared eclipse data, and also in one night of observations at J-band out ofeclipse. The oscillation amplitude, in all infrared bands except Ks, is aboutthe same as in the optical. However, the stellar oscillations in Ks band haveabout twice the amplitude as seen in the optical, possibly because theBrackett-gamma line falls in this bandpass. We use our best-fit values for theeclipse depth, as well as the 0.9 micron eclipse observed by Smith et al., toexplore possible states of the exoplanetary atmosphere, based on the method ofMadhusudhan and Seager. On this basis we find two possible states for theatmospheric structure of WASP-33b. One possibility is a non-invertedtemperature structure in spite of the strong irradiance, but this modelrequires an enhanced carbon abundance (C/O>1). The alternative model has solarcomposition, but an inverted temperature structure. Spectroscopy of the planetat secondary eclipse, using a spectral resolution that can resolve the watervapor band structure, should be able to break the degeneracy between these verydifferent possible states of the exoplanetary atmosphere. However, both ofthose model atmospheres absorb nearly all of the stellar irradiance withminimal longitudinal re-distribution of energy, strengthening the hypothesis ofCowan et al. that the most strongly irradiated planets circulate energy poorly.Our measurement of the central phase of the eclipse yields e*cos(omega)=0.0003+/-0.00013, which we regard as being consistent with a circular orbit.

Infrared Eclipses of the Strongly Irradiated Planet WASP-33b, and Oscillations of its Host Star