Spitzer Space TelescopeObservations of Magnetic Cataclysmic Variables: Possibilities for the Presence of Dust in Polars

We present Spitzer Space Telescope photometry of six short-period polars, EFEri, V347 Pav, VV Pup, V834 Cen, GG Leo, and MR Ser. We have combined theSpitzer Infrared Array Camera (3.6 -8.0 microns) data with the 2MASS J, H, K_sphotometry to construct the spectral energy distributions of these systems fromthe near- to mid-IR (1.235 - 8 microns). We find that five out of the sixpolars have flux densities in the mid-IR that are substantially in excess ofthe values expected from the stellar components alone. We have modeled theobserved SEDs with a combination of contributions from the white dwarf,secondary star, and either cyclotron emission or a cool, circumbinary dust diskto fill in the long-wavelength excess. We find that a circumbinary dust disk isthe most likely cause of the 8 micron excess in all cases, but we have beenunable to rule out the specific (but unlikely) case of completely opticallythin cyclotron emission as the source of the observed 8 micron flux density.While both model components can generate enough flux at 8 microns, neither dustnor cyclotron emission alone can match the excess above the stellar componentsat all wavelengths. A model combining both cyclotron and dust contributions,possibly with some accretion-generated flux in the near-IR, is probablyrequired, but our observed SEDs are not sufficiently well-sampled to constrainsuch a complicated model. If the 8 micron flux density is caused by thepresence of a circumbinary dust disk, then our estimates of the masses of thesedisks are many orders of magnitude below the mass required to affect CVevolution.Comment: 58 pages, 14 figures, ApJ accepte