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Astron. Astrophys. 354, 411-422 (2000)

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Research Note

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

Stefanie Komossa 1 and Janek Meerschweinchen 2

1 Max-Planck-Institut für Extraterrestrische Physik, Postfach 1603, 85740 Garching, Germany
2 Weststrasse 19, 31683 Obernkirchen 2, Germany

Received 8 April 1999 / Accepted 5 November 1999


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 properties. We focus on QSO 0117-2837, RX J0134-4258, and NGC 4051, and briefly comment on Mrk 1298 and 4C +74.26. The individual objects were originally partly selected as candidates to host warm absorbers on the basis of (i) characteristic 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 [FORMULA]-[FORMULA] diagram), and (iii) drastic spectral variability (RX J0134-4258). The temporal analysis reveals large-amplitude variability by a factor [FORMULA]30 in the long-term X-ray lightcurve of NGC 4051, very rapid variability of Mrk 1298, constant X-ray flux of the NLSy1 galaxy QSO 0117-2837, and constant mean countrate of RX J0134-4258 despite huge spectral changes. Besides the warm absorber, several further mechanisms and their merits/shortcomings are investigated to explain the spectral characteristics of the individual objects. Different models are favored for different sources. Consequences for Narrow-line Seyfert 1s in general are discussed and we present results from photoionization models to distinguish between different suggested NLSy1 scenarios.

Key words: galaxies: active – galaxies: nuclei – galaxies: quasars: general – galaxies: Seyfert – X-rays: galaxies

Send offprint requests to: St. Komossa (skomossa@xray.mpe.mpg.de)

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© European Southern Observatory (ESO) 2000

Online publication: February 9, 2000