Spitzer IRS Spectroscopy of Intermediate Polars: Constraints on Mid-Infrared Cyclotron Emission

Abstract

We present Spitzer Infrared Spectrograph (IRS) observations of eleven intermediate polars (IPs). Spectra covering the wavelength range from 5.2 to 14 $\mu$m are presented for all eleven objects, and longer wavelength spectra are presented for three objects (AE Aqr, EX Hya, and V1223 Sgr). We also present new, moderate resolution (R $\sim$ 2000) near-infrared spectra for five of the program objects. We find that, in general, the mid-infrared spectra are consistent with simple power laws that extend from the optical into the mid-infrared. There is no evidence for discrete cyclotron emission features in the near- or mid-infrared spectra for any of the IPs investigated. If cyclotron emission is occurring in the 5.2 to 14.0 $\mu$m bandpass it constitutes less than 1% of the bolometric luminosity of any of the IPs. We discuss our results in the context of the standard model for IPs.

arXiv comment43 pages, including 17 figures, accepted by the Astrophysical Journal

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