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 N_H ~ 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 M _BH estimated from the M _BH-velocity dispersion relation, the source size is D _S < 20R_G and the distance and density of the obscuring clouds are R ~ 3000-10, 000R_G 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 ~10R_G ) of the accretion disk, in agreement with the small source size inferred from the analysis of the absorption variability.