ROSAT X-Ray Observations of Four Planetary Nebulae

Abstract

We report ROSAT Position Sensitive Proportional Counter (PSPC) observations of four planetary nebulae. The observations show that all four nebulae have two-component spectra. A two-component model consisting of a blackbody and a Raymond-Smith thermal plasma is fitted to the observed ROSAT PSPC spectra of NGC t535, Abell 36, and NGC 7293. For all three cases, the temperatures of the blackbody component are apparently higher than those of the stellar photo spheres, indicating nonblackbody atmospheres. In all cases, the temperatures of the high-energy component can be attributed to a hot plasma associated with the possible stellar coronae or the "hot bubbles" predicted by the interacting winds model. The spectral energy distribution of NGC t535 is constructed and modeled by incorporating our X-ray spectrum into existing data in UV, optical, near-infrared, and far-infrared wavelengths.