X-ray emission/absorption mechanisms of 4 NLSy-1-like AGN and a radio quasar - QSO 0117-2837, RX J0134.3-4258, NGC 4051, Mrk 1298, 4C+74.26

We present a study of the X-ray variability properties and spectral shapes of five active galaxies all of which show extreme or enigmatic X-ray proper ties. We focus on QSO 0117-2837, RX J0134-4258, and NGC 4051, and briefly c omment on Mrk 1298 and 4C +74.26. The individual objects were originally pa rtly selected as candidates to host warm absorbers on the basis of (i) char acteristic X-ray absorption features (NGC 4051, Mrk 1298, 4C +74.26), (ii) extreme X-ray spectral steepness (QSO 0117-2837; this object is found to be located in the 'zone of avoidance' when plotted in the Gamma(x)-FWHMH beta diagram), and (iii) drastic spectral variability (RX J0134-4258). The temp oral analysis reveals large-amplitude variability by a factor similar to 30 in the long-term X-ray lightcurve of NGC 4051, very rapid variability of M rk 1298, constant X-ray flux of the NLSy1 galaxy QSO 0117-2837, and constan t mean countrate of RX J0134-3258 despite huge spectral changes. Besides th e warm absorber, several further mechanisms and their merits/shortcomings a re investigated to explain the spectral characteristics of the individual o bjects. Different models are favored for different sources. Consequences fo r Narrow-line Seyfert Is in general are discussed and we present results fr om photoionization models to distinguish between different suggested NLSy1 scenarios.