Variable partial covering and a relativistic iron line in NGC 1365

TL;DR

This paper analyzes X-ray observations of NGC 1365, revealing a variable partial covering cloud and a relativistic iron line, providing insights into the structure of the AGN's inner regions.

Contribution

It presents the first detailed analysis linking rapid X-ray absorption variability with the detection of a relativistic iron line in NGC 1365.

Findings

Obscuring cloud crossing time of ~25 ks implies a compact X-ray source.

Detection of a relativistic iron line indicating emission from within ~10 R_G.

High iron abundance (~3x solar) in the accretion disk.

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 January 2004. The two main results are: 1) We detect an obscuring cloud with N_H~3.5x10^23 cm^(-2) crossing the line of sight in ~25 ks. This implies a dimension of the X-ray source not larger than a few 10^13 cm and a distance of the obscuring cloud of the order of 10^16 cm. Adopting the black hole mass M(BH) estimated from the M(BH)-velocity dispersion relation, the source size is D_S<20 R_G and the distance and density of the obscuring clouds are R~3000-10000 R_G and n~10^(10) 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 (~3 times solar) and an origin of these components in the inner part (~10 R_G) of the accretion disk, in agreement with the small source size inferred from the analysis of the absorption variability.