TITLE: GCN CIRCULAR NUMBER: 42215 SUBJECT: GRB 251013B: Fermi GBM Final Real-time Localization DATE: 25/10/13 08:33:39 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 08:24:27 UT on 13 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251013B (trigger 782036672.403254 / 251013350).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 356.5, Dec = 7.5 (J2000 degrees, equivalent to J2000 23h 45m, 7d 30'), with a statistical uncertainty of 5.7 degrees.

The angle from the Fermi LAT boresight is 87.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013350/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/bn251013350/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013350/q...

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