TITLE: GCN CIRCULAR NUMBER: 42012 SUBJECT: GRB 250926B: Fermi GBM Final Localization DATE: 25/09/26 21:05:58 GMT FROM: Matt Godwin msg0028@uah.edu

The Fermi GBM team reports the detection of a likely LONG GRB

"At 19:50:31.07 UT on 26 September 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250926B (trigger 780609036/250926827).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 291.66, Dec = -80.93 (J2000 degrees, equivalent to J2000 19h 26m, -80d 55'), with a statistical uncertainty of 7.60 degrees.

The angle from the Fermi LAT boresight is 23 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250926827/q...

The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250926827/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250926827/q..."

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