The impact of SUZAKU on the knowledge of The Physics of CVs

Abstract

Suzaku satellite observed dozens of WD binaries and gave us various findings and knowledge. In this paper, four topics are picked up. (1) From a nova outburst of V2491 Cyg, a very hard non-thermal component with Γ= 0.1 $\pm$0.2 was found. Mass accretion seemed to be rekindled 30 days after the nova and its X-ray spectrum is similar to that of intermediate polars. (2) In a nova outburst of a symbiotic Mira star V407 Cyg, a non-equilibrium ionization (NEI) plasma emission was found, which shows asymmetry in the environment encountered by the nova ejecta. The coincidental GeV γ-ray decline/X-ray rise can be explained by the stalling of the shock front because of the ejecta running into the red giant photosphere. (3) X-ray spectra of five symbiotic stars (CD-28 3719, Hen 3-1591, Hen 3-461, EG And and 4 Dra) have hot thermal plasma of $T_{\rm max}$ > 3 keV. To reproduce thetemperature, X-ray energy source should be ascribed to release of the gravitational potential in boundary layers. (4) X-ray spectrum of γ Cas can be reproduced by a single-temperature thermal plasma model of 15 keV. X-ray dips of order of 10$^4$ s can be explained by partial covering absorption. A WD binary is more likely for γ Cas identity because of its spectrum without power-law component and consistency of the covering fractions of absorbers and dip duration.