TITLE: GCN CIRCULAR NUMBER: 42196 SUBJECT: GRB 251011B: Fermi GBM Final Real-time Localization DATE: 25/10/11 07:19:01 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 07:08:21 UT on 11 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251011B (trigger 781859306.91454 / 251011297).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 5.3, Dec = -56.1 (J2000 degrees, equivalent to J2000 00h 21m, -56d 06'), with a statistical uncertainty of 5.3 degrees.

The angle from the Fermi LAT boresight is 78.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011297/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/bn251011297/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011297/q...

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