AstroNote 2026-116

AT 2026kqq (ZTF26aaufnkd) was reported to TNS on 2026-04-25 (2026TNSTR1828....1S) and is located in the nearby galaxy NGC 4532, which has a redshift-independent distance of ~10.7 Mpc (Sorce+ 2014). We obtained spectroscopic observations using the Gemini Multi-Object Spectrograph (GMOS) at the Gemini South Observatory on 2026-04-26 03:35:24 UTC through Gemini Program GS-2026A-Q-122 (PI Jacobson-Galan). The spectrum shows Balmer series emission lines extending to ~1500 km/s. These profiles show weaker absorption components with absorption minima at ~2500 km/s but with the profile extending to ~4000 km/s. We also identify weaker He I P Cygni profiles. Based on these characteristics, we classified this source on TNS as a “SN imposter” (i.e., similar to AT 2016blu and AT 2000ch). 

The most recent ZTF photometry reveals that the transient has a red color (g - r ≈ 0.5 mag) and its present r-band absolute magnitude is -11.5 mag based on the Tully-Fisher host galaxy distance. The line of sight MW extinction is small (0.02 mag) and there appears to be minimal host extinction based on the Na ID absorption, implying that the red color is intrinsic to the source. The transient appears to show a periodic ZTF light curve extending back to first detection in 2018. AT 2026kqq is coincident with the position of AT 2017des. The overall spectral appearance, luminosity, and light-curve evolution are consistent with both LBV-like eruptions (Smith et al. 2011) and supernova precursor events seen before Type IIn SNe (e.g., Pastorello et al. 2013, N. L. Strotjohann et al. 2021). We encourage continued spectroscopic follow-up of this source and thank the Gemini staff for their help in observing this target. 

This AstroNote is 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; and OKC, University of Stockholm, Sweden. Operations are conducted by Caltech's Optical Observatory (COO), Caltech/IPAC, and the University of Washington at Seattle, USA.