2009ApJ...690.1522B

Spitzer and Caltech Submillimeter Observatory images and spectrophotometry of ε Eridani at wavelengths from 3.5 to 350 µm reveal new details of its bright debris disk. The 350 µm map confirms the presence of a ring at r = 11''-28''(35-90 AU), observed previously at longer sub-mm wavelengths. The Spitzer mid-IR and far-IR images do not show the ring, but rather a featureless disk extending from within a few arcsec of the star across the ring to r∼ 34'' (110 AU). The spectral energy distribution (SED) of the debris system implies a complex structure. A model constrained by the surface brightness profiles and the SED indicates that the sub-mm ring emission is primarily from large (a∼ 135 µm) grains, with smaller (a∼ 15 µm) grains also present in and beyond the ring. The Spitzer Infrared Spectrograph and Multiband Imaging Photometer for Spitzer SED-mode spectrophotometry data clearly show the presence of spatially compact excess emission at λ ≳ 15 µm that requires the presence of two additional narrow belts of dust within the sub-mm ring's central void. The innermost belt at r∼ 3 AU is composed of silicate dust. A simple dynamical model suggests that dust produced collisionally by a population of about 11 M_⊕ of planetesimals in the sub-mm ring could be the source of the emission from both in and beyond the sub-mm ring. Maintaining the inner belts and the inner edge to the sub-mm ring may require the presence of three planets in this system including the candidate radial velocity object.