AstroNote 2025-70

AT2025bpq passed the BTSBot filter (Rehemtulla et al. 2024) of ZTF and was discovered on 2025-02-15 at an apparent r-band magnitude of 18.16. We classify AT2025bpq/ZTF25aafofmu as a type IIn supernova based on the spectrum taken by Nordic Optical Telescope (ALFOSC) on 24-02-2025. The spectra was taken with gr4 (NOT, ALFOSC; resolution 360) with an exposure time of 40 minutes. 

The SN shows flash ionized signatures of  C III/N III around 4700 Angstrom along with intermediate width H$\alpha$ and H$\beta$ emission signatures (FWHM ~ 1300 km/sec).  The redshift estimated from the host galaxy lines of ZTF25aafofmu is 0.0637. NGSF (AstroNote 2022-191; Howell et al. 2005) also shows a best match with SN IIn/II-flash. The line width is narrower than typical TDEs and rise time is also quite fast at the given absolute magnitude which rules out the TDE scenario. 

We want to remark that the spectrum suffers from host galaxy contribution (0.4" separated) with a peak absolute magnitude of -20.2. The NOT spectrum was obtained ~8 days after the first ZTF detection. The exceptionally long-lasting flash features, suggests that this is a type IIn and not an infant SN spectrum. Further follow-up of this SN is encouraged.