AstroNote 2026-172

AT 2026ngr (ZTF26aaxhpdm) was discovered by the Zwicky Transient Facility (ZTF) on 2026 May 15 and was subsequently identified as a candidate strongly gravitationally lensed supernova on 2026 May 28 (AstroNote 2026-156).

On 2026 May 30 UT, we obtained a near-infrared spectrum (containing 4 x 530s exposures) of the transient using the Folded port InfraRed Echellette (FIRE) spectrograph in Echelle mode (covering the 0.8–2.5 μm wavelength range) on the 6.5m Magellan Baade telescope (MJD = 61190.158). The spectrum confirms SN 2026ngr is a Type Ia supernova around maximum luminosity at a source redshift of z = 0.95, as determined by cross-correlating the data using SNID.

Assuming this redshift, the spectrum exhibits prominent Si II λ5972, Si II λ6355, and Ca II near-infrared triplet features with an expansion velocity of ~12,000 km/s. The spectrum is well-matched by templates of both normal Type Ia and subluminous (SN 1986G-like) Type Ia supernovae close to light-curve maximum. Assuming a normal Type Ia supernova luminosity, the observed brightness implies that the supernova is highly magnified (>50×) by the foreground lensing galaxy.

Further photometric and spectroscopic follow-up is strongly encouraged to robustly determine the specific subtype and to monitor the evolution of possible multiple images.

We sincerely thank the support astronomer Gonzalo Díaz and the telescope operator Fernanda Milla at Las Campanas observatory for supporting our Magellan observation.