The reanalysis of the ROSAT data of classical nova V1974 Cygni 1992

Abstract

The ROSAT PSPC data (0.1-2.4 keV) have been reanalyzed in order to understand the development of the classical nova V1974 Cygni 1992 after outburst in the X-ray wavelengths. The X-ray spectrum is fit with a two-component model. The first component is a white dwarf atmosphere emission model developed for the remnants of classical novae near the Eddington luminosity. The model is used to fit the soft X-ray data in similar to 0.1-1.0 keV range. The second component is a Raymond-Smith model of thermal plasma applied to the hard X-ray emission above similar to 1.0 keV. The results verify the standard nova theory that the radius of the stellar remnant decreases as the effective temperature increases at constant bolometric luminosity. The hard X-ray component is found to evolve independently from the soft one. The time evolution of the hard X-ray flux and the plasma temperatures decreasing from 10 keV to 1 keV suggest emission from shock heated gas as the origin of the hard component.