X-ray absorption variability in NGC 4507

TL;DR

This study analyzes X-ray spectral data from NGC 4507 over six months, revealing absorption variability due to parsec-scale gas clouds, indicating complex and non-universal absorber structures in this AGN.

Contribution

It provides the first detailed spectral analysis showing variability in X-ray absorption linked to parsec-scale clouds, challenging simple models of AGN obscurers.

Findings

Absorption varies on 1.5 to 4 months timescales.

No significant short-term variability detected.

Absorber structure is complex and not solely BLR clouds or torus.

Abstract

We present a complete spectral analysis of an XMM-Newton and Chandra campaign of the obscured AGN in NGC 4507, consisting of six observations spanning a period of six months, ranging from June 2010 to December 2010. We detect strong absorption variability on time scales between 1.5 and 4 months, suggesting that the obscuring material consists of gas clouds at parsec-scale distance. The lack of significant variability on shorter time scales suggests that this event is not due to absorption by broad line region clouds, which was instead found in other studies of similar sources. This shows that a single, universal structure of the absorber (either BLR clouds, or the parsec-scale torus) is not enough to reproduce the observed complexity of the X-ray absorption features of this AGN.