EUV and Soft X-ray Observations of the Seyfert Galaxies MRK 279, MRK 478, and TON S180

We present light curves and spectra of three Seyfert galaxies in the EUV and soft X-ray ranges. The data were obtained from EUVE and ROSAT observations of the galaxies MRK 279, MRK 478 and TON S180. The variability in the light curves provides an upper limit to the size of the EUV-soft X-ray emitting region which excludes the BLR and diffuse intercloud regions as the source of this emission. The EUV spectra are all characterized by discrete line features; on the other hand, the soft X-ray spectra are well described by a single power law with ISM absorption from the Milky Way. Comparing the EUV spectra in their rest frames, we find that several of these features appear at the same wavelengths. A composite EUV spectrum is produced from these redshift-corrected spectra. The most striking feature in the composite spectrum is an emission feature at ~ 79 Angstroms, which is also observed in the spectra of each of the individual galaxies. We discuss several possible mechanisms for this emission features.