Herschel Observations and Updated Spectral Energy Distributions of Five Sunlike Stars with Debris Disks

Abstract

Observations from the Herschel Space Observatory have more than doubled the number of wide debris disks orbiting Sunlike stars to include over 30 systems with R > 100 AU. Here we present new Herschel PACS and re-analyzed Spitzer MIPS photometry of five Sunlike stars with wide debris disks, from Kuiper belt size to R > 150 AU. The disk surrounding HD 105211 is well resolved, with an angular extent of >14" along the major axis, and the disks of HD 33636, HD 50554, and HD 52265 are extended beyond the PACS PSF size (50% of energy enclosed within radius 4.23"). HD 105211 also has a 24-micron infrared excess that was previously overlooked because of a poorly constrained photospheric model. Archival Spitzer IRS observations indicate that the disks have small grains of minimum radius ~3 microns, though the minimum grain gradius is larger than the radiation pressure blowout size in all systems. If modeled as single-temperature blackbodies, the disk temperatures would all be <60 K. Our radiative transfer models predict actual disk radii approximately twice the radius of model blackbody disks. We find that the Herschel photometry traces dust near the source population of planetesimals. The disk luminosities are in the range 0.00002 <= L/L* <= 0.0002, consistent with collisions in icy planetesimal belts stirred by Pluto-size dwarf planets.