AstroNote 2026-277

We report near-infrared YJHs-band photometry of the very nearby Type Ia-CSM supernova SN 2026sqf in NGC 3310, obtained with the MDM InfraRed Astronomy InGaAs Experiment (MIRAGE) instrument on the MDM 1.3-m telescope. MIRAGE is a new robotic YJHs InGaAs imager in routine operations since March 2026 (Ibrahim & De 2026).

The observations were carried out on UT 2026 September 20 (MJD 61303.52), approximately 74 days after discovery, and shortly following solar conjunction. The data are reduced as part of an automated pipeline (De et al. 2020) including astrometric and photometric calibration against the PS1 and 2MASS catalogs. We measure magnitudes of Y = 12.122 ± 0.002 AB mag, J = 11.448 ± 0.002 Vega mag, and H = 10.898 ± 0.003 Vega mag. Adopting a distance of 17.8 Mpc (Rehemtulla et al., AstroNote 2026-240), the corresponding absolute magnitudes are M_Y = −19.1, M_J = −19.8, and M_H = −20.4 mag. 

SN 2026sqf is substantially brighter than normal SNe Ia in the infrared, with its luminosity comparable to those of strongly interacting SNe Ia-CSM such as SN 2005gj (Prieto et al. 2007). Recent Chandra observations detected luminous X-ray emission from SN 2026sqf, providing evidence for ongoing interaction with dense circumstellar material (CSM; Margutti et al., AstroNote 2026-275). We measure a relatively red J − H color of 0.55 mag, compared with other nearby events e.g. J − H ~ 0.2 mag for SN 2005gj (Prieto et al. 2007) at a similar phase. The high NIR luminosity together with the red color may be indicative of hot dust emission as seen in other SNe Ia-CSM (Fox et al. 2013, Szalai et al. 2021, Sharma et al. 2023, Mo et al. 2025). 

We encourage continued multi-wavelength follow-up observations, particularly infrared spectroscopy to characterize the possible circumstellar dust emission. Further MIRAGE monitoring of SN2026sqf is planned. 

We thank the Mt Cuba Astronomical Foundation for supporting the development of MIRAGE, and the MDM Observatory staff for support of operations.