We present results from spectral analysis of ASCA data on the strong Feii narrow-line Seyfert 1 galaxy Mrk 507. This galaxy was found to have an exceptionally flat ROSAT spectrum among the narrow-line Seyfert 1 galaxies (NLS1s) studied by Boller, Brandt & Fink (1996). The ASCA spectrum however shows a clear absorption feature in the energy band below 2 keV, which partly accounts for the flat sp...

We have used the WGA catalog of ROSAT PSPC X-ray sources to study the X-ray spectrum of about 500 quasars in the redshift interval 0.1–4.1, detected with a signal to noise better than 7. We have parameterized the PSPC spectrum in terms of two ‘effective energy spectral indices’, αS (0.1-0.8 keV), and αH (0.42.4 keV), which allows for the different Galactic NH along the quasars line of sight. We...

ROSAT is the first mission to have detected X-ray emission in radio galaxies which are both powerful (/17s gHz > 1027 W Hz -1 sr -~) and distant (z > 0.4). enabling tests of "unified schemes" through a comparison of the X-ray and radio properties of powerful quasars and radio galaxies. These radio galaxies are faint in X-rays, but, nevertheless, ROSAT is capable of resolving any associated Xray...

We have compiled an X-ray catalog of optically selected rich clusters of galaxies observed by the PSPC during the pointed GO phase of the ROSAT mission. This paper contains a systematic X-ray analysis of 150 clusters with an optical richness classification of R ≥ 2 from the ACO catalog (Abell, Corwin, and Olowin 1989). All clusters were observed within 45 of the optical axis of the telescope du...

We have developed a local-detect algorithm using the Mexican-Hat function as a lter to detect X-ray sources in the 3-dimensional space-time domain. Our method takes advantage of the limited spatial and frequency extents of the Mexican-Hat function to allow the correlation to be done in pieces small enough to be handled on standard workstations. We apply this algorithm to ROSAT PSPC data of the ...