Contributed Talk - Splinter eROSITA

Wednesday, 14 September 2022, 14:44   (SFG 0140 / virtual eROSITA)

An ultra-soft nuclear transient in a FRII radio galaxy discovered with eROSITA

luliia Grotova, Arne Rau, Adam Malyali, Zhu Liu, Andrea Merloni
Max-Planck-Institut für extraterrestrische Physik, Gießenbachstraße 1, 85748 Garching, Germany

The SRG/eROSITA all-sky survey provides a unique opportunity to explore various high-energy astrophysical phenomena. Due to its superior sensitivity and wide field-of-view, we have compiled a growing sample of X-ray selected nuclear transients, including those without prior signs of AGN activity. In this talk we would like to present the discovery and multi-wavelength follow-up of the transient ultra-soft X-ray source eRASSt_J093641.9+111347 associated with an FRII radio galaxy at redshift of z=0.127. Being one of the brightest soft nuclear transients found with eROSITA, it has brightened and faded by more than a factor of 10 on the scale of months. The archival and follow-up optical spectroscopic observations of the counterpart revealed optical spectra typical of a quiescent galaxy with no signatures of emission lines. The soft X-ray spectrum and significant short-term variability are unusual for FRII galaxies, however, make the source a promising candidate Tidal Disruption Event. We discuss the origin of this peculiar event in the context of X-ray variability of FRII galaxies.