2010ApJ...714..549H

We have assembled new Spitzer Space Telescope IRAC observations of the mysterious binary star ε Aurigae, along with archival far-ultraviolet to mid-infrared data, to form an unprecedented spectral energy distribution (SED) spanning 3 orders of magnitude in wavelength from 0.1 µm to 100 µm. The observed SED can be reproduced using a three-component model consisting of a 2.2^+0.9_–0.8M_☉F-type post-asymptotic giant branch star, and a 5.9±0.8 M_☉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 R_☉ for the F star, consistent with published interferometric observations. The dusty disk is constrained to be viewed at an inclination of i ≳ 87°, and has an 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 µm 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 {Lt}1 M_☉. We discuss evolutionary scenarios for this system that could lead to the current status of the stellar components and suggest possibilities for its future evolution, as well as potential observational tests of our model.