  We have assembled new Spitzer Space Telescope Infrared Array Camera
observations of the mysterious binary star Epsilon Aurigae, along with archival
far-ultraviolet to mid-infrared data, to form an unprecedented spectral energy
distribution spanning three orders of magnitude in wavelength from 0.1 microns
to 100 microns. The observed spectral energy distribution can be reproduced
using a three component model consisting of a 2.2+0.9/-0.8 Msun F type
post-asymptotic giant branch star, and a 5.9+/-0.8 Msun B5+/-1 type main
sequence star that is surrounded by a geometrically thick, but partially
transparent, disk of gas and dust. At the nominal HIPPARCOS parallax distance
of 625 pc, the model normalization yields a radius of 135+/-5 Rsun for the F
star, consistent with published interferometric observations. The dusty disk is
constrained to be viewed at an inclination of i > 87 deg, and has effective
temperature of 550+/-50 K with an outer radius of 3.8 AU and a thickness of
0.95 AU. The dust content of the disk must be largely confined to grains larger
than ~10 microns in order to produce the observed gray optical-infrared
eclipses and the lack of broad dust emission features in the archival Spitzer
mid-infrared spectra. The total mass of the disk, even considering a potential
gaseous contribution in addition to the dust that produces the observed
infrared excess, is << 1 Msun. We discuss evolutionary scenarios for this
system that could lead to the current status of the stellar components and
suggests possibilities for its future evolution, as well as potential
observational tests of our model.
