How complex is the obscuration in AGN? New clues from the Suzaku monitoring of the X-ray absorbers in NGC7582

TL;DR

This study uses Suzaku observations of NGC7582 to reveal rapid X-ray absorption variability, suggesting a more complex AGN obscuration structure than traditional models, involving multiple absorbers at different scales.

Contribution

It introduces a revised AGN unification model incorporating multiple absorbers, including a near-BH material and a galactic-scale dust lane, to explain observed spectral variability.

Findings

Rapid column density changes occur on timescales less than a day.

A constant Compton-thick component is present, not along the line of sight.

Multiple absorbers at different scales are needed to explain the data.

Abstract

We present the results of a Suzaku monitoring campaign of the Seyfert 2 galaxy, NGC7582. The source is characterized by very rapid (on timescales even lower than a day) changes of the column density of an inner absorber, together with the presence of constant components arising as reprocessing from a Compton-thick material. The best fitting scenario implies important modifications to the zeroth order view of Unified Models. While the existence of a pc-scale torus is needed in order to produce a constant Compton reflection component and an iron K$\alpha$ emission line, in this Seyfert 2 galaxy this is not viewed along the line of sight. On the other hand, the absorption of the primary continuum is due to another material, much closer to the BH, roughly at the distance of the BLR, which can produce the observed rapid spectral variability. On top of that, the constant presence of a $10^{22}$ cm$^{-2}$ column density can be ascribed to the presence of a dust lane, extended on a galactic scale, as previously confirmed by Chandra. There is now mounting evidence that complexity in the obscuration of AGN may be the rule rather than the exception. We therefore propose to modify the Unification Model, adding to the torus the presence of two further absorbers/emitters. Their combination along the line of sight can reproduce all the observed phenomenology.