Suzaku observations of Fe Kalpha line in some hard X-ray emitting symbiotic stars and magnetic cataclysmic variables
Abstract
We present the Suzaku observations of Fe Kalpha for four Hard X-ray emitting symbiotic stars (hSSs) and 19 magnetic cataclysmic variables (mCVs). The 6.7 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 have surveyed the emission using a collection of Suzaku observations of hSSs and mCVs to better understand the geometry of these systems. We find that they do not seem to have a single geometry, and that while absorption-induced fluorescence leads to some emission in three hSSs and 12 mCVS, there are strong hints that significant 6.4 keV emission arises in the accretion disk irradiated by the hard X-rays from the boundary layer between the accretion disk and hot white dwarf, in the case of hSSs (SS73 17). For mCVs, the 6.4 keV line emission arises from the reflection of hard X-rays from the white dwarf surfaces in 5 mCVs. This suggests there could be relevant information about the geometry of the WD in the system encoded in the Fe Kalpha line.
- Publication:
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Memorie della Societa Astronomica Italiana
- Pub Date:
- 2015
- Bibcode:
- 2015MmSAI..86...96E
- Keywords:
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- Stars: hard X-rays;
- emission lines