ABSTRACT: We present the first mid-infrared (5.5–14.5 microns) spectrum of a highly magnetic cataclysmic variable, EF Eridani, obtained with the Infrared Spectrograph on the Spitzer Space Telescope. The spectrum displays a relatively flat, featureless continuum. A spectral energy distribution model consisting of a 9500 K white dwarf, L5 secondary star, cyclotron emission corresponding to a B∼13 MG white dwarf magnetic field, and an optically thin circumbinary dust disk is in reasonable agreement with the extant 2MASS, IRAC, and IRS observations of EF Eri. Cyclotron emission is ruled out as a dominant contributor to the infrared flux density at wavelengths >3 microns. The spectral energy distribution longward of 5 microns is dominated by dust emission. Even longer wavelength observations would test the model's prediction of a continuing gradual decline in the circumbinary disk-dominated region of the spectral energy distribution.

Spectral energy distribution of EF Eri showing the 2MASS JHK_s (black points) and Spitzer IRAC 3.5–8.0 micron (blue points) photometry from Brinkworth et al. (2007, ApJ, 659, 1541), a ground-based near-infrared spectrum (green line; from Harrison et al. 2007, ApJ, 656, 444), and our new Spitzer IRS spectrum (red line). On the photometric data points, the vertical error bars are 1σ standard deviations of the flux densities; the horizontal “error bars” show the band width.