Variable partial covering and a relativistic iron line in NGC 1365

Abstract

We present a complete analysis of the hard X-ray (2-10 keV) properties of the Seyfert galaxy NGC 1365, based on a 60 ks XMM-Newton observation performed in 2004 January. The two main results are as follows. (1) We detect an obscuring cloud with Nh ∼ 3.5 × 1023 cm-2 crossing the line of sight in ∼25 ks. This implies a dimension of the X-ray source not larger than a few 1013 cm and a distance of the obscuring cloud of the order of 1016 cm. Adopting the black hole mass MBH estimated from the MBH-velocity dispersion relation, the source size is DS < 20Rg and the distance and density of the obscuring clouds are R ∼ 3000-10,000Rg and n ∼ 1010 cm -3, i.e., typical values for broad-line region clouds. (2) An iron emission line with a relativistic profile is detected with high statistical significance. A time-integrated fit of the line+continuum reflection components suggests a high iron abundance (approximately three times solar) and an origin of these components in the inner part (within ∼ 10Rg) of the accretion disk, in agreement with the small source size inferred from the analysis of the absorption variability. © 2009. The American Astronomical Society. All rights reserved. Printed in the U.S.A.