Iron Line Diagnostics of the Postshock Hot Plasma in Magnetic Cataclysmic Variables Observed with ASCA

The ASCA spectra of ~20 magnetic cataclysmic variables are presented. Owing to the high spectral resolution of the solid-state imaging spectrometer, we successfully resolved the iron Kα emission line into the fluorescent (6.4 keV) and plasma (6.7 and 7.0 keV) components. By comparing the ionization temperature, which is obtained from the intensity ratio of the plasma line components of iron, with the continuum temperature, we have obtained the evidence that the postshock plasma has a temperature distribution. Detailed analysis indicates that the observed temperature distribution is consistent with that expected from the postshock plasma model in the bremsstrahlung cooling domain. In the framework of this postshock plasma model, we have constrained the mass of the white dwarf in totally nine intermediate polars and obtained the iron abundances. The obtained masses are generally consistent with the previous X-ray work. We have found that the iron abundance is generally subsolar, and its distribution probably peaks at 0.2-0.6 solar. We have also shown that the reflection from the white dwarf surface makes significant contribution to the observed fluorescent iron Kα emission line.

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