6 papers · 1 filter
Gamma Rays from Compact Objects
Karl Mannheim
A review on some recent developments in gamma ray astrophysics with particular emphasis on the role of relativistic bulk motion in nonthermal gamma ray sources, radiation processes…
ROSAT PSPC observations of six PG quasars and PHL 1657
Joerg P. Rachen, Karl Mannheim, Peter L. Biermann
We report results from the spectral analysis of pointed ROSAT PSPC observations of six PG quasars and the weak-bump quasar PHL 1657. Disregarding other frequency bands, the PSPC da…
Ultrasoft transient X-ray emission from AGN
K. Mannheim, D. Grupe, K. Beuermann +2
We report some remarkable and unexpected results of optical/UV/X-ray follow-up observations of bright soft X-ray selected AGN from the ROSAT All-Sky-Survey. The majority of these A…
The origin of soft X-rays in luminous AGN
K. Mannheim, M. Schulte, J. Rachen
We predict that the UV bump spectrum of quasars extends into the soft X-ray range with a steep power law. For radio-louds, the spectral index is alpha_s ~ 1.7 (S_nu = S_o nu^-alpha…
Discovery of an ultrasoft transient ROSAT AGN: WPVS007
D. Grupe, K. Beuermann, K. Mannheim +3
We have identified the ROSAT source RX J0039.2-5117 with the previously almost unknown `narrow line' Seyfert 1 galaxy WPVS007 (z=0.028). The X-ray source displays quite unusual pro…
X-RAY OUTBURST OF THE PECULIAR SEYFERT GALAXY IC 3599
D. Grupe, K. Beuermann, K. Mannheim +4
We report optical, soft X-ray, and UV observations of the peculiar Seyfert galaxy IC 3599 using data obtained with ROSAT and IUE. Most remarkably, we discovered a rapid decrease of…