The EUV/X-ray spectrum of SS Cygni in outburst

Open Access
Publisher Website
Google Scholar
Abstract
The dwarf nova SS Cyg was observed during decline from outburst by the ROSAT observatory during its all-sky survey. In addition to data from the ROSAT Wide Field Camera (WFC) and Position Sensitive Proportional Counter (PSPC), we acquired two blocks of hard X-ray data from the Ginga Large Area Counter, extending our EUV/X-ray coverage over the band 0.06–15 keV. This wide band allows us to discriminate clearly the presence of two components in the spectrum: a soft component which decays more quickly than the optical flux, and a hard X-ray component which shows no overall trend through our observations. The soft component dominates the spectrum below 0.5 keV during outburst, and can be modelled as a blackbody with a temperature T≈ 20–25 eV. Its luminosity appears to be much less than that of the accretion disc, but considerably greater than the hard component luminosity, which is suppressed by a factor of four compared with that seen in quiescence. A strong iron emission line and absorption edge in the Ginga spectrum imply substantial covering of the hard X-ray emission region by highly ionized gas, which is hard to reconcile with the standard picture in which the hard X-rays arise from a hot corona.

This publication has 0 references indexed in Scilit: