AstroNote 2026-147

By combining ATLAS (  Tonry et al. 2018, (PASP,130:064505),  Smith et al. (2020, PASP, 132:08500)) and the  Pan-STARRS Survey for Transients (Chambers et al. arXiv 1612:05560, Fulton et al. 2025, MNRAS, 542, 541)  we report the discovery of a nearby young supernova, presumably within the first few hours of explosion,  observed to rise significantly within a 1hr quad of exposures. 

We discovered AT2026ngb in the 70Mpc galaxy NGC 4924, rapidly rising within 1hr of Pan-STARRS observations. The transient was detected in the first of 4 Pan-STARRS images w=19.77 +/- 0.09 on  MJD = 61179.32 (2026-05-19.32) with an absolute magnitude of M = -14.6 +/- 0.2.  The Pan-STARRS w-band quad data show the object brightened by 0.57 magnitudes in 55 minutes.  There was no ATLAS detection on the last observation of the field 27.7hrs before, to a limiting mag of approximately c < 20. Further ATLAS survey operations measured the source rising by to c = 18.6 +/- 0.1 on   MJD = 61180.11 (2026-05-20.11), at 19hrs after discovery. At the time of posting, the supernova is likely still within the first 24-48hrs after explosion. 

AT2026ngb is offset by 5.7 arcsec north, 9.4 arcsec east from NGC 4924, which is at z = 0.016 or d = 71 Mpc (from NED), implying an absolute magnitude of M = -14.6 (assuming m-M = 34.26 and A_w = 0.13) at discovery, and now at M = -15.8. Rapid followup observations are encouraged. A finder is attached. 

The discoveries from this program are a byproduct of the Pan-STARRS NEO survey observations. Operation of the Pan-STARRS1 and Pan-STARRS2 telescopes is primarily supported by the National Aeronautics and Space Administration under Grant No. NNX12AR65G and Grant No. NNX14AM74G issued through the SSO Near Earth Object Observations Program. Data are processed at Queen's University Belfast enabled through the STFC grants ST/P000312/1 and ST/T000198/1. 

The Asteroid Terrestrial-impact Last Alert System [ATLAS] project is primarily funded to search for Near-Earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO search include images and catalogs from the survey area. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889,  STFC grants ST/Y001605/1, ST/X001253/1, the Royal Society and Schmidt Sciences. ATLAS-Teide is an IAC instrument included in the present “Strategic plan of the Canarian Observatories”, funded by the European Union  NextGenerationEU  EQC2021-007122-P and ICT2022-007828 projects. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy,  Queen's University Belfast, University of Oxford, the Space Telescope Science Institute, the South African Astronomical Observatory, The Millennium Institute of Astrophysics (MAS), Chile, and the Instituto de Astrofisica De Canarias.