The WIRED Survey. IV. New Dust Disks from the McCook & Sion White Dwarf
  Catalog
  We have compiled photometric data from the Wide-field Infrared Survey
Explorer All Sky Survey and other archival sources for the more than 2200
objects in the original McCook & Sion Catalog of Spectroscopically Identified
White Dwarfs. We applied color-selection criteria to identify 28 targets whose
infrared spectral energy distributions depart from the expectation for the
white dwarf photosphere alone. Seven of these are previously known white dwarfs
with circumstellar dust disks, five are known central stars of planetary
nebulae, and six were excluded for being known binaries or having possible
contamination of their infrared photometry. We fit white dwarf models to the
spectral energy distributions of the remaining ten targets, and find seven new
candidates with infrared excess suggesting the presence of a circumstellar dust
disk. We compare the model dust disk properties for these new candidates with a
comprehensive compilation of previously published parameters for known white
dwarfs with dust disks. It is possible that the current census of white dwarfs
with dust disks that produce an excess detectable at K-band and shorter
wavelengths is close to complete for the entire sample of known WDs to the
detection limits of existing near-IR all-sky surveys. The white dwarf dust disk
candidates now being found using longer wavelength infrared data are drawn from
a previously underrepresented region of parameter space, in which the dust
disks are overall cooler, narrower in radial extent, and/or contain fewer
emitting grains.
