Comptonization As An Origin Of The Continuum In Intermediate Polars

In this paper we test if the similar to 0.3-15 keV XMM-Newton EPIC pn spectral continuum of IPs can be described by the thermal Comptonization compTT model. We used publicly observations of 12 IPs (AE Aqr, EX Hya, V1025 Cen, V2731 Oph, RX J2133.7+5107, PQ Gem, NY Lup, V2400 Oph, IGR J00234+6141, IGR J17195-4100, V1223 Sgr, and XY Ari). We find that our modeling is capable of fitting well the average spectral continuum of these sources. In this framework, UV/soft X-ray seed photons (with kT (s) of 0.096 +/- 0.013 keV) coming presumably from the star surface are scattered off by electrons present in an optically thick plasma (with kT (e) of 3.05 +/- 0.16 keV and optical depth tau of 9.5 +/- 0.6 for plane geometry) located nearby (on top) to the more central seed photon emission regions. A soft blackbody (bbody) component is observed in 5 out of the 13 observations analyzed, with a mean temperature kT ( bb ) of 0.095 +/- 0.004 keV. We observed that the spectra of IPs show in general two photon indices Gamma, which are driven by the source luminosity and optical depth. Low luminosity IPs show Gamma of 1.83 +/- 0.19, whereas high luminosity IPs show lower Gamma of 1.34 +/- 0.02. Moreover, the good spectral fits of PQ Gem and V2400 Oph indicate that the polar subclass of CVs may be successfully described by the thermal Comptonization as well.