An intense and broad Fe K line observed in the X-ray luminous quasar Q 0056-363 with XMM-Newton

Free access article

Issue		A&A Volume 408, Number 1, September II 2003


Page(s)		119 - 125
Section		Galactic structure and dynamics
DOI		http://dx.doi.org/10.1051/0004-6361:20030950

A&A 408, 119-125 (2003)
DOI: 10.1051/0004-6361:20030950

An intense and broad Fe K $_{\alpha}$ line observed in the X-ray luminous quasar Q 0056-363 with XMM-Newton

D. Porquet¹ and J. N. Reeves^{2, 3}

¹ Max-Plank-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
² Laboratory for High Energy Astrophysics, Code 662.0, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
³ Universities Space Research Association

(Received 12 March 2003 / Accepted 16 June 2003 )

Abstract
We present an XMM-Newton observation of the radio-quiet quasar Q0056-363 ( z=0.162). This is the first time that this quasar is observed in the hard X-ray range (above 2 keV). We find that Q0056-363 is a powerful X-ray quasar, with a 0.3-12 keV unabsorbed luminosity of about $1.2 \times 10^{45}$ erg s ^-1 with the largest part (~67%) emitted below 2 keV. The spectrum reveals a large featureless soft X-ray excess below 2 keV and a strong broad Fe K $_{\alpha}$ line at 6.4 keV (in the quasar frame). The Fe K $_{\alpha}$ line is due to low to moderate ionization states of iron (i.e., < $\ion{Fe}{xvii}$ ), with an equivalent width of about 250 eV and a velocity width of about 25 000 km s ^-1. Q0056-363 is presently the most luminous AGN known to exhibit such a broad and intense Fe K $_{\alpha}$ line profile from near neutral iron. The line can be fitted with a relativistic profile from an accretion disc around either a Schwarzschild (non-rotating) or a Kerr (rotating) black hole. A combination of two thermal Comptonization components and a disc reflection model is favored to explain both the continuum over the energy range 0.3-12 keV and the Fe K $_{\alpha}$ line. A patchy corona covering a large part of the inner disc surface is needed in order to be compatible with the accretion rate inferred from the spectral energy distribution of Q0056-363, unless the mass of the black hole is much higher than about $5\times10^{8}~M_{\odot}$ .

Key words: galaxies: active -- X-rays: galaxies -- accretion discs -- quasars: individual: Q0056-363

Offprint request: D. Porquet, dporquet@mpe.mpg.de

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