Dwarf Novae And Galactic Bulge X-ray Emission

Cataclysmic variables are very important in astronomy,which has important sig-nificance on theory of cataclysmic variables’ evolution and progenitor of type Ia super-nova.We have known some mechanisms of cataclysmic variables(e.g.structure and emission mechanisms of intermediate polar,fluorescent line from iron atoms etc.),but there are a few mechanisms we are not clear now,including bondary layer of dwarf novae.The emission of dwarf novae is mainly from optical-thin multi-temperature plasma.Outer edge of bondary layer may be composed of strong shock wave or a series of weak shock waves.Due to its difficulties in physics,it is usually assumed as strong shock wave,and it is supported by observations in allowable error.We introduce a new empirical correlation of Tmax-MWD in dwarf novae in the assumption of weak shock wave.Galactic diffuse X-ray emission is an unresolved emission distributed across the total Galactic plane,found in several years before.In the recent studies,the origin of 5-10keV X-ray emission from the Galactic bulge is relatively clear that may mainly come from non-magnetic cataclysmic variables(e.g.dwarf novae),and the emission of iron line FeXXV-Hea(6.7keV)and FeXXVI-Lya(7.0keV)is dominated by dwarf no-vae in Galactic bulge.There is a correlation of the intensity ratio of iron line I7.0/I6.7 and the maximum temperature in dwarf novae.Combining the empirical correlation of Tmax-MWD in dwarf novae and the correlation of I7,0/I6.7 and Tmax,we could derive the correlation of I7 0/I6.7 and MWD.We use the intensity ratio of iron line I7.0/I6.7 to derive the average white dwarf mass of cataclysmic variables in Galactic bulge to be 0.81 ± 0.07M☉,which is consistent with that in local cataclysmic variables.