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Soft X-ray properties of a high redshift sample of QSOs observed with ROSAT

G. C. Dewangan·K. P. Singh·K. F. Gunn·A. M. Newsam·I. M. McHardy·L. R. Jones
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Abstract

In order to study systematically the soft X-ray emission of Active Galactic Nuclei (AGNs) at medium to high redshifts, we have analyzed ROSAT PSPC and HRI data of QSOs at 0.26 3.0), one of which is a narrow-line QSO - a high luminosity version of narrow-line Seyfert 1 galaxies. The average photon index ( ) is 2.40+/-0.09 (with a dispersion of 0.57) in the 0.1-2 keV band. The average QSO spectra in four redshift bins flatten from an average photon index of ~ 2.53 at 0.25 < z < 1 to ~ 2 at 2 < z < 3.4. The flattening of the average photon index can be understood in terms of the redshift effect of the mean intrinsic QSO spectrum consisting of two components - a soft X-ray excess and a power-law component. We have also studied optical spectra of 12 of the 22 QSOs.

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G. C. Dewangan, K. P. Singh, K. F. Gunn, A. M. Newsam, I. M. McHardy, L. R. Jones. 2002-08-08. Soft X-ray properties of a high redshift sample of QSOs observed with ROSAT. https://doi.org/10.1046/j.1365-8711.2002.05946.x

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