Abstract

Contributed Talk - Splinter Multimessenger

Extreme ends of AGN variability

Sabina Bahic
Leibniz-Institut für Astrophysik Potsdam (AIP)

Active galactic nuclei (AGN) are among the most extreme variable sources in the Universe, emitting energy across the entire electromagnetic spectrum. While AGN variability has been observed for decades, the mechanisms driving it remain poorly understood. The development of time-domain astronomy, enabled by missions like eROSITA, has led to the discovery of new transient phenomena, including changing-look AGN, changing-state AGN (CS-AGN), and changing-obscuration AGN. These discoveries provide new insights into the complex nature of accretion onto supermassive black holes. While changing-state and changing-look AGN have been studied in other wavelengths, the work that will be shown in this talk represents the first large-scale statistical X-ray study of CS-AGN. Using eROSITA’s first and second all-sky surveys provide a unique time-domain perspective with a cadence of six months. The work is structured around two key objectives: improving the selection method for transient X-ray sources and conducting a statistical analysis of ignition (flux increase) and shut-down (flux decrease) events. Additionally, a robust optical follow-up campaign in combination with available multi-wavelength archival data were used to characterize our X-ray selected sample.