Abstract for Proposal 090428
Probing the nature of nuclear transients in quiescent galaxies found by eROSITA
During its all sky survey, eROSITA is detecting transients
associated with galaxy nuclei that show no signatures of prior
AGN activity. Whilst a significant fraction of these may be produced
by tidal disruption events (TDEs), initial results from follow-up
campaigns suggest that multiple different phenomena may generate
transients with observed properties similar to those expected from TDEs.
Here, we ask for XMM ToO observations of 8 new nuclear transients in
quiescent galaxies discovered by eROSITA in AO21. This will provide vital
information on the diversity of the spectral and temporal evolution
of this population, enabling an improved understanding of the X-ray
evolution of tidal disruption events, and/ or their imposters.
Details on Observing Strategy and Trigger Criteria
We ask to observe 8 TDE candidates to be discovered during the eROSITA all
sky survey. In order to avoid contamination from AGN ignition events,
the transients are selected following these criteria: the source
shall have no previous X-ray detection and the X-ray brightening has
to indicate at least amplitude of >10. The eROSITA X-ray spectrum
has to be ultra-soft and without a significant contribution from an
additional power law component. The multi-wavelength counterpart has
to be a galaxy not known to be an AGN (e.g., from WISE colors, SDSS
spectroscopy, etc.) and without significant historical variability at
UV/optical/near-IR wavelengths. We ask for ToO observations with EPIC
of the 8 targets, each with two visits of 20ks. The first observation of
each event will be triggered within 4 weeks after the eROSITA discovery,
while the second epoch will be requested to be performed as close as
possible to 6 months after the first.