AstroNote 2026-5

The nuclear transient AT 2025afsj was originally discovered in ZTF photometry on November 11, 2025, by the Fink group (AT Discovery Report 279229). It was subsequently also identified in GOTO photometry (November 27; AT Discovery Report 282673), and highlighted as a TDE candidate by POTICA (Concepcion et al., AstroNote 2025-341). 

Wu et al. (AstroNote 2025-348) classified the transient as a tidal disruption event (TDE) based on their identification of a broad emission component associated with HeII 4686A seen in a spectrum obtained on December 20, 2025, using YFOSC on the Lijiang 2.4 m telescope. Wu et al. pointed out that the host of the transient is the previously-known, broad-line active galactic nucleus (AGN) SDSS J125507.07+340846.6, located at z=0.1654, which was identified as such based on legacy SDSS spectroscopy obtained in April 2004.

Following these reports, we obtained two new Las Cumbres Observatory FLOYDS spectra,  on January 9 and 13, 2026, using the Faulkes Telescope North, at the Haleakalā Observatory. Our spectra show spectral features that are more consistent with those seen in the class of Bowen Fluorescence Flares (BFFs; identified by Trakhtenbrot et al. 2019, Nature Astronomy, 3, 242) than those seen in typical TDEs (e.g. van Velzen et al. 2020, SSRv, 216, 124). In particular, we highlight the presence of the OIII 3133A emission line and the HeII 4686A + NIII 4640A blend, which is narrower, and less symmetric, than what is seen in TDEs. Compared with the archival SDSS spectrum, the nuclear flare exhibits much stronger broad Balmer emission (in Hgamma and Hdelta), and much bluer continuum emission (as noted by Wu et al.). 

Thus, AT 2025afsj joins other BFFs associated with previously-known (broad-line) AGN, i.e. already-active SMBHs with existing circumnuclear structures of high-density ionized gas, with the most robust examples being AT 2021loi (Makrygianni et al. 2023; ApJ 953, 32) and AT 2019aalc (Sniegowska et al. 2025; ApJ 989, 173).