The first large area survey of eROSITA unveiled a small set of Active Galactic Nuclei with unusually steep and flat spectral slopes. In the calibration period and the all-sky survey eROSITA also revisited well-known X-ray sources. We report on an automated detection of spectral changes in the X-ray sky compared to archival observations, based on the XMM-Newton, Chandra and Swift archives. The bona fide differences can be grouped into 1) drastic steepening of the intrinsic corona power law and 2) occultation of the corona by an intervening cloud. We will discuss the underlying physics and how to probe them through follow-up with X-ray and optical telescopes. The large-scale eRASS monitoring for occultation events in particular are a promising tool to constrain the granularity of the nuclear obscurer.
|Presenter status||eROSITA consortium member|