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Issue A&A
Volume 365, Number 1, January I 2001
First Results from XMM-Newton
Page(s) L116 - L121
DOI 10.1051/0004-6361:20000423



A&A 365, L116-L121 (2001)
DOI: 10.1051/0004-6361:20000423

The first XMM-Newton spectrum of a high redshift quasar - PKS 0537-286

J. N. Reeves1, M. J. L. Turner1, P. J. Bennie1, K. A. Pounds1, A. Short1, P. T. O'Brien1, Th. Boller2, M. Kuster3 and A. Tiengo4.

1  X-Ray Astronomy Group, Department of Physics and Astronomy, Leicester University, Leicester LE1 7RH, UK
2  Max-Planck-Institut für extraterrestrische Physik, Postfach 1603, 85748 Garching, Germany
3  Institut für Astronomie und Astrophysik - Astronomie, University of Tübingen, Waldhäuser Strasse 64, 72076 Tübingen, Germany
4  IFC Milan, 20133 Milano, Italy

(Received 2 October 2000 / Accepted 17 October 2000)

Abstract
We present XMM-Newton observations of the high redshift (z=3.104), radio-loud quasar PKS 0537-286. The EPIC CCD cameras provide the highest signal-to-noise spectrum of a high-z quasar to date. The EPIC observations show that PKS 0537-286 is extremely X-ray luminous ( $L_{\rm X}=2$ 1047 erg s-1), with an unusually hard X-ray spectrum ( $\Gamma=1.27\pm0.02$). The flat power-law emission extends over the whole observed energy range (0.4 to 40 keV in the quasar rest frame); there is no evidence of intrinsic absorption, which has been claimed in PKS 0537-286 and other high z quasars. However, there is evidence for weak Compton reflection. A redshifted iron K line, observed at 1.5 keV - corresponding to $\sim$6.15 keV in the quasar rest frame - is detected at 95% confidence. If confirmed, this is the most distant iron K line known. The line equivalent width is small (33 eV), consistent with the "X-ray Baldwin effect" observed in other luminous quasars. The reflected continuum is also weak ($R \la$0.25). We find the overall spectral energy distribution of PKS 0537-286 is dominated by the X-ray emission, which, together with the flat power-law and weak reflection features, suggests that the X-radiation from PKS 0537-286 is dominated by inverse Compton emission associated with a face-on relativistic jet.


Key words: galaxies: active -quasars: individual: PKS 0537-286 -X-rays: galaxies

Offprint request: J. N. Reeves, jnr@star.le.ac.uk

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