A radio flare associated with the nuclear transient eRASSt J234403−352640: an outflow launched by a potential tidal disruption event

Abstract

We present an extensive radio monitoring campaign of the nuclear transient eRASSt J234402.9−352640 with the Australia Telescope Compact Array, one of the most X-ray luminous TDE candidates discovered by the SRG/eROSITA all-sky survey. The observations reveal a radio flare lasting >1000 d, coincident with the X-ray, UV, optical, and infrared flare of this transient event. Through modelling of the 10 epochs of radio spectral observations obtained, we find that the radio emission is well-described by an expanding synchrotron emitting region, consisting of a single ejection of material launched coincident with the optical flare. We conclude that the radio flare properties of eRASSt J234402.9−352640 are consistent with the population of radio-emitting outflows launched by non-relativistic tidal disruption events, and that the flare is likely due to an outflow launched by a tidal disruption event (but could also be a due to a new AGN accretion event) in a previously turned-off AGN.