The ionised X-ray outflowing torus in ESO 323-G77: low-ionisation clumps confined by homogeneous warm absorbers

TL;DR

This study analyzes X-ray spectra of ESO 323-G77 over multiple years, revealing homogeneous warm absorbers and a colder, variable component, all located within the torus, advancing understanding of AGN outflows and their structure.

Contribution

It provides detailed characterization of multiple ionized absorbers in ESO 323-G77, highlighting their homogeneity, variability, and spatial relation within the AGN torus, which is a novel detailed multi-epoch analysis.

Findings

Two warm absorbers are stable over time, indicating a homogeneous outflow.

A colder absorber varies on long timescales and responds to nuclear luminosity changes.

All absorbers are likely co-spatial within the dusty torus, sharing the same pressure.

Abstract

We report on the long- and short-term X-ray spectral analysis of the polar-scattered Seyfert 1.2 galaxy ESO 323-G77, observed in three epochs between 2006 and 2013 with Chandra and XMM-Newton. Four high-resolution Chandra observations give us a unique opportunity to study the properties of the absorbers in detail, as well as their short time-scale (days) variability. From the rich set of absorption features seen in the Chandra data, we identify two warm absorbers with column densities and ionisations that are consistent with being constant on both short and long time-scales, suggesting that those are the signature of a rather homogeneous and extended outflow. A third absorber, ionised to a lesser degree, is also present and it replaces the strictly neutral absorber that is ubiquitously inferred from the X-ray analysis of obscured Compton-thin sources. This colder absorber appears to vary in column density on long time-scales, suggesting a non-homogeneous absorber. Moreover, its ionisation responds to the nuclear luminosity variations on time-scales as short as a few days, indicating that the absorber is in photoionisation equilibrium with the nuclear source on these time-scales. All components are consistent with being co-spatial and located between the inner and outer edges of the so-called dusty, clumpy torus. Assuming co-spatiality, the three phases also share the same pressure, suggesting that the warm / hot phases confine the colder, most likely clumpy, medium. We discuss further the properties of the outflow in comparison with the lower resolution XMM-Newton data.