Extremely luminous X-ray ignition detected by eROSITA: AGN variability or TDE
Abstract
The SRG/eROSITA scanning mission allows for all-sky time domain searches for dramatic changes in the inner accretion flow around supermassive black holes. These changes provide unique insights into nuclear transients as well as into the mechanisms powering extreme AGN variability. In SRG/eROSITA's second all-sky survey a new, bright object was discovered. With an increase in X-ray flux by a factor of at least 35, this is among the strongest extragalactic ignition events discovered by SRG/eROSITA in its first year of operation. The optical counterpart is an extragalactic object at z=0.1 located in a group of four galaxies. In this talk I will present the results of our multi-wavelength follow-up of the ignition event. Our extensive X-ray followup with XMM-Newton, NICER, and Swift reveals a source with a soft X-ray spectrum and strong variability in its luminosity, on timescales as short as hours. Optical spectra show a blue continuum and broad Hα and Hβ emission lines with strongly asymmetric features, indicative of an outflow. The optical light curve shows a rapid rise and stays relatively flat in the first months after the ignition, before starting to decay. The object has features typical of an AGN, as well as of a TDE. I will discuss the possible origin of the event in the context of both possibilities.
- Publication:
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44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.2192H