AstroNote 2024-379

As part of the ongoing development of a TDE identification pipeline for the Fink collaboration, we have identified AT 2020ukj as a candidate TDE. It was previously reported to TNS and missclassified as a SN candidate (https://www.wis-tns.org/object/2020ukj/discovery-cert, see the ZTF lightcurve at https://fink-portal.org/ZTF20accxwrk).

The two other most possible interpretations for such a transient are a slow TDE or an episode of flaring activity from an AGN. An optical spectrum obtained from the Caucasian Mountain Observatory 2.5m telescope (Shatsky et al. 2020) revealed a spectrum roughly consistent with a passive galaxy at z=0.066, that does not contain any emission lines. While TDEs can show a purely thermal ‘featureless’ optical spectrum, AGNs are expected to show emission lines. This thus excludes the latter possibility, and supports the interpretation that this source is a TDE. This would be one of, if not the slowest decaying optical TDE to date. This source thus has significant potential in constraining the current models.

We will request X-ray follow-up with Swift, and additional follow-up is encouraged.