TITLE: GCN CIRCULAR NUMBER: 41993 SUBJECT: GRB 250926A: Fermi GBM Final Real-time Localization DATE: 25/09/26 00:31:52 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM do_not_reply@GIOC.nsstc.nasa.gov

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

At 00:21:23 UT on 26 Sep 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250926A (trigger 780538888.96614 / 250926015).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 83.0, Dec = -7.0 (J2000 degrees, equivalent to J2000 05h 31m, -7d 00'), with a statistical uncertainty of 1.8 degrees.

The angle from the Fermi LAT boresight is 79.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250926015/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/bn250926015/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250926015/q...

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