Taming the Invisible Monster: The Disk of Epsilon Aurigae in the Far-Infrared

We propose to obtain photometric flux density measurements of the remarkable binary star Epsilon Aurigae in all six of the PACS and SPIRE imaging bands. Epsilon Aur is seen close to edge on, and has long (2 yr) eclipses every 27.1 yr. The last eclipse, during 19821984, received worldwide attention from astronomers. During 20092011, the system is again in eclipse and is the focus of a worldwide observing campaign enlisting both professional and amateur astronomers. Epsilon Aur consists of a high luminosity postAGB F0 star with a much less luminous stellar companion. The latter is newly proven by us to be surrounded by a solar systemsized disk of cool dust. This disk is a rare example of an evolved disk, composed of the remnants of the endgame of stellar evolution, rather than a primordial disk as found in T Tauri stars and A stars like Beta Pic. Gaps in the Epsilon Aur disk, reminiscent of the structure of the rings of Saturn, were recently inferred from groundbased timeseries spectroscopic observations. By analogy to the role of shepherd moons in the rings of Saturn, this suggests that there could be planetesimals, dwarf planets, or even fullsize terrestrial planets in the Epsilon Aur disk. The spectral energy distribution of Epsilon Aur is wellsampled from the farUV to the midIR (0.170 microns), with one radio measurement at 1200 microns. However, it is currently unconstrained in the wavelength region spanned by PACS and SPIRE, which is dominated by the dust disk. These Herschel instruments are uniquely configured to provide high S/N photometry bridging the gaps between the midIR and radio regimes. These SED points are crucial to confirm if a nonblackbody slope is present, relating to dust grain emissivity, and if potentially bright emission features from molecular species might dominate. These observations will contribute to understanding stellar evolution in binary stars, as well as the formation, evo truncated!, [truncated!, Please see actual data for full text]