2026/07/30 by Isaiah S. Cox, Núria Torres-Albà, Stefano Marchesi +5
Physics and Astronomy · #astro-ph.GA #astro-ph.HE
17 pages, 5 figures, 4 tables, submitted to ApJ
arxiv created 2026/07/30 · arxiv updated 2026/07/31
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 (NH) to be measured. Many sources display NH 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 NH variability increases with the number of observations available. Additionally, the observed magnitudes of the NH variability depend on the timescale between observations. In this work, we present the NH variability analysis of NGC 1142, which has a total of nine X-ray observations over ∼20 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.