AstroNote 2025-67

We report the classification of optical transient ZTF25aafofcs / AT 2025bri as a tidal disruption event (TDE). The source was selected by the tdescore ML classifier (Stein+2024, doi: 10.3847/2041-8213/ad3337) as a candidate TDE, primarily due to its blue colour, nuclear location and the lack of AGN-like host signatures. It was independently selected as a candidate TDE by NEEDLE (Sheng+ 2024, doi: 10.1093/mnras/stae1253). 

ZTF25aafofcs / AT2025bri was first detected by ZTF on 2025-02-15 as an alert, and reported as a transient to TNS on the same day by ALeRCE. The transient was rising at the time of discovery, and has remained persistently blue (g-r=-0.2). Forced photometry reveals an additional early detection of this source on 2025-02-04. The candidate was first identified as a likely TDE by tdescore on 2025-02-20, and assigned for spectroscopic follow-up.

A spectrum of ZTF25aafofcs was taken with the Goodman High Throughput Spectrograph on the 4m SOAR telescope on 2025-02-22 (PI: Andreoni), which exhibited a blue continuum. A redshift of z=0.061 was derived from weak narrow nebular emission lines from the host galaxy. A broad feature consistent with He II 4686 at this redshift is also present. 

ZTF25aafofcs has a current magnitude of mg=17.8 on 2025-02-22, but we emphasize that the transient has not yet reached peak. With the apparent redshift, the magnitude of ZTF25aafofcs is currently Mg=-19.5. 

The luminosity, spectrum, lightcurve evolution, and nuclear location are all indicative of a TDE origin for this flare. We therefore classify ZTF25aafofcs/AT2025bri as a likely TDE-He.

ToO observations have been requested with the Neil Gehrels Swift Observatory,

Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; Operations are conducted by Caltech's Optical Observatory (COO), Caltech/IPAC, and the University of Washington at Seattle, USA.