TITLE:   GCN CIRCULAR
NUMBER:  42923
SUBJECT: GRB 251201B: Fermi GBM Final Real-time Localization
DATE:    25/12/01 16:37:01 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 16:26:24 UT on 1 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251201B (trigger 786299189.217446 / 251201685).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 13.8, Dec = -40.0 (J2000 degrees, equivalent to J2000 00h 55m, -40d 00'), with a statistical uncertainty of 1.1 degrees.

The angle from the Fermi LAT boresight is 118.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251201685/quicklook/glg_skymap_all_bn251201685.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251201685/quicklook/glg_healpix_all_bn251201685.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251201685/quicklook/glg_lc_medres34_bn251201685.gif