X-ray Absorption Variability in NGC 1142: Another Constraint on the Nature of the Torus/Broad-Line Region in Active Galactic Nuclei
arXiv:2607.28501
The paper analyzes nine X‑ray observations of the active galaxy NGC 1142 over ~20 years to study changes in line‑of‑sight column density, using torus models to infer the geometry and dynamics of the obscuring material.
Abstract
The physics, geometry, and kinematics of the gas and dust surrounding the central engine of active galactic nuclei (AGN) are not well understood. In some sources, this material obscures the coronal X-ray emission, allowing its line-of-sight column density () to be measured. Many sources display variability across multiple epochs. Studying this variability can provide information about the distribution and dynamics of the obscuring material. Particularly, previous works have shown that the probability of observing variability increases with the number of observations available. Additionally, the observed magnitudes of the variability depend on the timescale between observations. In this work, we present the variability analysis of NGC 1142, which has a total of nine X-ray observations over years, including five from a NuSTAR+XMM-Newton monitoring campaign performed in 2024-2025 and reported here for the first time. We use the physically-motivated torus models UXCLUMPY, XSKIRTor, and RXTorusD to model the spectra. Our results confirm the previously observed trends, and we compare these trends to simulated obscuration curves assuming different locations and distributions of obscuring clouds.
17 pages, 5 figures, 4 tables, submitted to ApJ