Abstract for Proposal 090399

XMM follow-ups of rare AGN ignition and shut-down events detected with eROSITA

eROSITA is performing multiple all-sky X-ray surveys until 2023, and our team is systematically identifying rare accretion ignition/shut-down events - changing-look AGN - as they are transitioning. To track how the X-ray corona, UV/optical accretion disk, and optical broad-line region respond to a sudden, major change in accretion rate, we propose joint ToO observations of XMM-Newton (EPIC+OM) and VLT (FORS2) to obtain at least two observations per triggered object (maximum of 4 ignition events and 4 shutdown events). We will constrain the extent of these drastic flux changes and yield crucial constraints on how the different structural AGN components respond to dramatic changes of the accretion rate.

Details on Observing Strategy and Trigger Criteria
Trigger criteria: 15 ks ignition ToO: i) flux increase by a factor >10 compared to previous eRASS scans and ii) 3sigma significance of the change and iii) X-ray position must match with a previous AGN/galaxy 50 ks shutdown ToO: i) flux decrease by a factor >10 compared to previous eRASS scans and ii) 3sigma significance of the change and iii) X-ray position must match with a previous AGN reaction time: for ignition and shutdown ToOs: up to 10 days observing strategy: single ToO (single observation joint with VLT/FORS2) ignition ToO: primary instrument PN, small window mode; OM: UVM2 filter shutdown ToO: primary instrument PN, full window mode; OM: UVM2 filter