Suzaku Observations of the Dwarf Nova SS Cyg in Quiescence and Outburst

We present results from the Suzaku observations of the dwarf nova SS Cyg in quiescence and outburst in 2005 November. High sensitivity of the HXD PIN and high spectral resolution of the XIS enable us to determine plasma parameters with unprecedented precision. The maximum temperature of the plasma in quiescence 20.4+4.0 −2.6 keV is significantly higher than that in outburst 6.0+0.2 −1.3 keV. The elemental abundances of oxygen and iron are both subsolar (0.46+0.04 −0.03Z and 0.37 +0.01 −0.03Z , respectively). The solid angle of cold reflecting matter subtending over an optically thin thermal plasma is Ω/2π = 1.7 ± 0.2 in quiescence. A 6.4 keV iron Kα line is resolved into narrow and broad components. These facts indicate that both the white dwarf and the accretion disk contribute to the reflection. We consider the standard optically thin boundary layer as the most plausible picture for the plasma configuration in quiescence. The solid angle of the reflector in outburst Ω/2π = 0.9+0.5 −0.4 and a broad 6.4 keV iron line indicate that the reflection in outburst occurs at the surface of the accretion disk. The broad 6.4 keV line suggests that the optically thin thermal plasma is distributed over the accretion disk like solar coronae.