  We observe two secondary eclipses of the strongly irradiated transiting
planet WASP-33b in the Ks band, and one secondary eclipse each at 3.6- and 4.5
microns using Warm Spitzer. This planet orbits an A5V delta-Scuti star that is
known to exhibit low amplitude non-radial p-mode oscillations at about
0.1-percent semi-amplitude. We detect stellar oscillations in all of our
infrared eclipse data, and also in one night of observations at J-band out of
eclipse. The oscillation amplitude, in all infrared bands except Ks, is about
the same as in the optical. However, the stellar oscillations in Ks band have
about twice the amplitude as seen in the optical, possibly because the
Brackett-gamma line falls in this bandpass. We use our best-fit values for the
eclipse depth, as well as the 0.9 micron eclipse observed by Smith et al., to
explore possible states of the exoplanetary atmosphere, based on the method of
Madhusudhan and Seager. On this basis we find two possible states for the
atmospheric structure of WASP-33b. One possibility is a non-inverted
temperature structure in spite of the strong irradiance, but this model
requires an enhanced carbon abundance (C/O>1). The alternative model has solar
composition, but an inverted temperature structure. Spectroscopy of the planet
at secondary eclipse, using a spectral resolution that can resolve the water
vapor band structure, should be able to break the degeneracy between these very
different possible states of the exoplanetary atmosphere. However, both of
those model atmospheres absorb nearly all of the stellar irradiance with
minimal longitudinal re-distribution of energy, strengthening the hypothesis of
Cowan 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.
