AstroNote 2025-74

We report the classification of optical transient ZTF25aacnkte/AT2025axp as a tidal disruption event (TDE). ZTF25aacnkte/AT2025axp was first detected by ZTF on 2025-01-21 as an alert, and reported as a transient to TNS on 2025-02-05. The transient was rising at the time of discovery with flat color in g-r, and is currently post-peak with no clear color evolution. ATLAS forced photometry reveals additional early detections of this source.

The first spectrum of ZTF25aacnkte was taken with the Goodman High-Throughput Spectrograph (GHTS) at the 4.1-meter Southern Astrophysical Research (SOAR) Telescope on 2025-02-24 (PI: Andreoni), revealing a broad feature likely associated with He II 4686. Narrow Ca II H and K absorption features are visible, placing the transient and its host at z = 0.1045. A second spectrum was taken with the DeVeny spectrograph on the 4.3-m Lowell Discovery Telescope (LDT) on 2025-02-27 (PI: Stein), which revealed the same broad He II feature, a blue continuum, and stellar absorption features which confirm the redshift.

The luminosity, spectrum, light curve evolution, and nuclear location are all indicative of a TDE origin for this flare. We therefore classify ZTF25aacnkte/AT2025axp as a likely TDE of the TDE-He subclass.

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

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.