Variable X-ray absorption in the mini-BAL QSO PG 1126-041

TL;DR

This study reveals complex, variable X-ray absorption features in the mini-BAL QSO PG 1126-041, showing fast outflows and spectral variability that inform models of AGN winds and accretion disk physics.

Contribution

First multi-epoch, time-resolved X-ray spectroscopy of a mini-BAL QSO, demonstrating variable ionized absorbers and outflows, advancing understanding of AGN wind dynamics.

Findings

Detected highly ionized outflows at v ~ 16500 km/s

Observed spectral variability on timescales of hours to months

Identified variable ionized absorbers affecting the optical-X-ray spectrum

Abstract

X-ray studies of active galactic nuclei (AGN) with powerful nuclear winds are important for constraining the physics of the inner accretion/ejection flow around supermassive black holes (SMBHs) and for understanding the impact of such winds on the AGN environment. Our main scientific goal is to constrain the properties of the circum-nuclear matter close to the SMBH in the mini-broad absorption line quasar (mini-BAL QSO) PG 1126-041 using a multi-epoch observational campaign with XMM-Newton. We performed temporally resolved X-ray spectroscopy and simultaneous UV and X-ray photometry on the most complete set of observations and on the deepest X-ray exposure of a mini-BAL QSO ever. We found complex X-ray spectral variability on time scales of both months and hours, which is best reproduced by means of variable massive ionized absorbers along the line of sight. As a consequence, the observed optical-to-X-ray spectral index is found to be variable with time. In the highest signal-to-noise observation we detected highly ionized X-ray absorbing material outflowing much faster (v ~ 16500 km/s) than the UV absorbing one (v ~ 5000 km/s). This highly ionized absorber is found to be variable on very short (a few kiloseconds) time scales. Our findings are qualitatively consistent with line-driven accretion disk winds scenarios. Our observations have opened the time-resolved X-ray spectral analysis field for mini-BAL QSOs. Only with future deep studies will we be able to map the dynamics of the inner flow and understand the physics of AGN winds and their impact on the environment.