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Issue A&A
Volume 398, Number 1, January IV 2003
Page(s) 81 - 87
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20021608



A&A 398, 81-87 (2003)
DOI: 10.1051/0004-6361:20021608

XMM-Newton observation of PG 0844+349

W. Brinkmann1, D. Grupe2, G. Branduardi-Raymont3 and E. Ferrero2

1  Centre for Interdisciplinary Plasma Science, Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
2  Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
3  Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey, RH5 6NT, UK

(Received 6 May 2002 / Accepted 4 November 2002 )

Abstract
In a ~20 ksec XMM-Newton observation the X-ray transient radio-quiet quasar was found in a historically high state compared to previous X-ray observations. The quasar showed a featureless spectrum with a strong soft excess over the extrapolation of a hard power law. Comptonization models or a broken power law with $\Gamma_{\mathrm {soft}} \sim 2.75$, $\Gamma_{\mathrm {hard}} \sim 2.25$ and a break energy of $E_{\mathrm {break}} \sim 1.35$ keV represent acceptable descriptions of the spectral continuum. In the Comptonization models the temperature of the Comptonizing gas is considerably lower than generally found in (broad line) Seyfert galaxies whereas the optical depth is much higher. As a similar behavior has been seen in NLSy1 galaxies, it might be an indicator of the different physical conditions in these two classes of AGN. During the XMM-Newton observation the flux of varied achromatically in a smooth, nearly linear fashion, by $\sim $25% on time scales of a few thousand seconds, which puts some constraints on current models of Comptonizing accretion disk coronae.


Key words: galaxies: active -- quasars: individual: PG 0844+349 -- X-rays: galaxies

Offprint request: W. Brinkmann, wpb@rzg.mpg.de

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© ESO 2003


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