AstroNote 2026-114

Two very nearby transient candidates (2026kid at 16.5 Mpc & 2026kie at 20.3 Mpc) were discovered the week of 19 April 2026. Here, we report on our follow-up observations of these transients.

SN 2026kid (ZTF26aatswhm) was discovered and first reported to TNS by Yasuo Sano on 22 April 2026 at 14:49:22 UTC (MJD=61152.62). It is coincident with NGC 5906 which has z=0.002218 (Springob+05), a Tully-Fisher measured distance of D=16.5 Mpc (Sorce+14) and a distance modulus of 31.09 mag. The earliest reported detection on TNS comes from the Zwicky Transient Facility (ZTF; Bellm+19), which measured 2026kid to m = 18.74 +/- 0.096 mag (M = -12.35 mag) in the r-band at MJD=61151.37. A ZTF r-band non-detection down to m=20.67 mag at MJD=61150.43 constrains the ZTF first detection to likely be <~1 day after first light. Following detections from ZTF have shown that SN 2026kid has risen rapidly at ~1.4 mag per day: m = 15.93 +/- 0.034 mag (M = -15.16 mag) in r-band at MJD=61153.39. 

We obtained spectroscopic follow-up of SN 2026kid with MMT/Binospec at MJD=61153.30. The spectrum indicates SN 2026kid is likely a considerably reddened Type II SN interacting with CSM. Emission features in He II 4686, C IV 5801 & 5812, N IV 7115 identified in the spectrum are typical of Type II SNe interacting with CSM. Strong Na ID doublet absorption at the redshift of the host galaxy provides consistent, independent evidence that the SN is indeed substantially reddened by its host. A NOT/ALFOSC spectrum ~one day later at MJD=61154.00 shows that the emission features identified in the Binospec data are still present. A Type IIn classification cannot be definitively ruled out at this point, so we encourage continued spectroscopic monitoring to finalize the classification of this target. LT/IOO photometric follow-up in the urgriz bands measures a strong red color: the g-r color at MJD=61154.06 is 0.72 mag.

LT/IOO follow-up of SN 2026kid

SN 2026kie (ZTF26aatzrft) was first reported to TNS at 16:06:45 UTC on 22 April 2026 by the Asteroid Terrestrial-impact Last Alert System (ATLAS; Tonry+18). SN 2026kie is coincident with NGC 3437 which has z=0.0038 (from host lines in follow-up spectrum) and a Tully-Fisher measured distance of D=20.3 Mpc (Sorce+14) corresponding to a distance modulus of 31.54 mag. The ATLAS discovery image measured m = 18.09 +/- 0.097 mag in o-band (M = -13.45 mag) at MJD=61152.31 following an o-band non-detection at MJD=61151.33 with limiting magnitude 19.49 mag, also implying a rapid ~1.4 mag/day rise.

We obtained spectroscopic follow-up of SN 2026kie with MMT/Binospec (MJD=61153.26) and LT/SPRAT (MJD=61152.94) as well as ugriz photometry with LT/IOO. These data reveal that 2026kie is also subject to significant host reddening (g-r ~ 0.65 mag; strong Na ID absorption at host redshift). Similar to Bostroem et al. who reported a Gemini/GMOS spectrum to TNS, we are unable to produce a confident subtyping of the transient, but the Binospec data also disfavor SN 2026kie being a H-rich SN.

LT/IOO follow-up of SN 2026kie

We sincerely thank the MMT observers for quickly obtaining these data.

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.