XMM-Newton unveils the complex iron Kα region of Mrk 279

¹ SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands e-mail: e.costantini@sron.nl
² Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht, The Netherlands
³ Department of Physics, Western Michigan University, Kalamazoo, MI 49008, USA
⁴ Department of Physics, Virginia Tech, Blacksburg, VA 24061, USA
⁵ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁶ University of Oxford, St John's College Research Centre, Oxford, OX1 3JP, UK

Received: 22 May 2009
Accepted: 14 January 2010

Abstract

We present the results of a ~160 ks-long XMM-Newton observation of the Seyfert 1 galaxy Mrk 279. The spectrum shows evidence of both broad and narrow emission features. The Fe Kα line may be equally well explained by a single broad Gaussian (FWHM ~ 10 000 km s^-1) or by two components: an unresolved core plus a very broad profile (FWHM ~ 14 000 km s^-1). For the first time we quantified, via the “locally optimally emitting cloud” model, the contribution of the broad line region (BLR) to the absolute luminosity of the broad component of the Fe Kα at 6.4 keV. We find that the contribution of the BLR is only ~3%. In the two-line component scenario, we also evaluated the contribution of the highly ionized gas component, which produces the Fe xxvi line in the iron K region. This contribution to the narrow core of the Fe Kα line is marginal <0.1%. Most of the luminosity of the unresolved, component of Fe Kα may come from the obscuring torus, while the very-broad associated component may come from the accretion disk. However, models of reflection by cold gas are difficult to test because of the limited energy band. The Fe xxvi line at 6.9 keV is consistent to be produced in a high column density (N_H ~ 10²³ cm^-2), extremely ionized (log ξ ~ ) gas. This gas may be a highly ionized outer layer of the torus.