Suzaku observations of Fe K α line in some Magnetic Cataclysmic Variables

Abstract

We resolved the 6.4 keV, 6.7 keV and 7.0 keV Fe K α lines in 19 Magnetic Cataclysmic Variables (mCVs) observed with the Suzaku satellite. The 6.7 keV and 7.0 keV emission lines are typically created by collisional excitation in the vicinity of the white dwarf arising from the shock front. The 6.4 keV iron emission line in contrast is formed in equilibrium by irradiation of the neutral (or low ionized) iron by a hard X-ray source, as a collisional origin would lead to rapid ionization. We study the emission of these lines in the 19 mCVs and found that the 6.4 keV line emission is likely created by a combination of reflection of hard X-rays from the white dwarf surfaces and absorption-induced fluorescence. Specifically, while absorption-induced fluorescence is dominant in 14 mCVs, there are significant hints that the 6.4 keV line emission arise from the reflection of hard X-rays from the white dwarf surfaces in 5 mCVs. This reflection suggests there could be relevant information about the geometry of the WD in the system encoded in the Fe K α line.