  We report secondary eclipse photometry of two hot Jupiters, WASP-48b and
HAT-P-23b, at 3.6 and 4.5 um taken with the InfraRed Array Camera aboard the
Spitzer Space Telescope during the warm Spitzer mission and in the H and Ks
bands with the Wide Field IR Camera at the Palomar 200-inch Hale Telescope.
WASP-48b and HAT-P-23b are Jupiter-mass and twice Jupiter-mass objects orbiting
an old, slightly evolved F star and an early G dwarf star, respectively. In the
H, Ks, 3.6 um, and 4.5 um bands, respectively, we measure secondary eclipse
depths of 0.047% +/- 0.016%, 0.109% +/- 0.027%, 0.176% +/- 0.013%, and 0.214%
+/- 0.020% for WASP-48b. In the Ks, 3.6 um, and 4.5 um bands, respectively, we
measure secondary eclipse depths of 0.234% +/- 0.046%, 0.248% +/- 0.019%, and
0.309% +/- 0.026% for HAT-P-23b. For WASP-48b and HAT-P-23b, respectively, we
measure delays of 2.6 +/- 3.9 minutes and 4.0 +/- 2.4 minutes relative to the
predicted times of secondary eclipse for circular orbits, placing 2-sigma upper
limits on |e cos(omega)| of 0.0053 and 0.0080, both of which are consistent
with circular orbits. The dayside emission spectra of these planets are
well-described by blackbodies with effective temperatures of 2158 +/- 100 K
(WASP-48b) and 2154 +/- 90 K (HAT-P-23b), corresponding to moderate
recirculation in the zero albedo case. Our measured eclipse depths are also
consistent with one-dimensional radiative transfer models featuring varying
degrees of recirculation and weak thermal inversions or no inversions at all.
We discuss how the absence of strong temperature inversions on these planets
may be related to the activity levels and metallicities of their host stars.
