Abstract for Proposal 086277
eROSITA follow-up of rare and dramatic changes in AGN
eROSITA, successfully launched in mid-2019, will perform multiple
all-sky X-ray surveys. Monitoring roughly half a million AGN/quasars,
eROSITA will identify rare, accretion ignition/depletion events as they
occur. To explore how the X-ray corona and accretion disk respond to
a sudden, major change in accretion rate, the identified sources need
medium signal to noise XMM-Newton ToO (EPIC+OM) observations to derive
meaningful spectral constraints. Thus, we propose 10 ToOs (five with
10 ks -- ignition event; five with 60 ks -- depletion event) each joint
with VLT FORS2 imaging and spectroscopy (for each ToO 1 hour) for optical
counterpart localization and tracking the Broad Line Region's responses.
Details on Observing Strategy and Trigger Criteria
A) ignition event (10 ks): flux increases by a factor of at least 10
compared to previous eRASS scans AND 3sigma significance of the change
AND flux after ignition at least f0.5-10keV ~ 1x10-12 cgs AND X-ray
position must match with a previous AGN/quasar/galaxy from catalogs; B)
depletion event (60 ks): flux decrease by a factor of at least 10 compared
to previous eRASS scans AND 3sigma significance of the change AND flux
before depletion at least f0.5-10keV ~ 1x10-12 cgs AND X-ray position
must match with a previous AGN/quasar catalog; Reaction time: up to 15
days after the request (the earlier the better); Observing strategy:
XMM-Newton observation with OM UVM2 joined by a VLT/FORS2 observation