4 NEW ACTIVE GALAXIES WITH STEEP SOFT-X-RAY SPECTRA

We have discovered four AGN in the ROSAT allsky-survey data with very steep X-ray spectra. We apply several models to these X-ray spectra wi th emphasis on warm absorber models which give an adequate description of the data. We report on the follow-up optical and radio observation s which allow the identification of three of these objects as Narrow L ine Seyfert 1 galaxies, and the fourth as BL Lac object. We have measu red small-FWHM H beta lines, strong FeII emission and weak [OIII] emis sion in the three Narrow Line Seyfert 1 galaxies, in line with known c orrelations with respect to the steepness of the X-ray spectra. We hav e discovered strong optical variability in the BL Lac object and two o f the Seyfert galaxies using photographic plates of the Sonneberg Obse rvatory field patrol. We finally discuss the statistical implications of our search algorithm on the expected number density of soft X-ray s elected AGN and conclude that up to 30% of X-ray selected AGN might: h ave supersoft X-ray spectra.