TITLE:   GCN CIRCULAR
NUMBER:  42525
SUBJECT: GRB 251031A: Fermi GBM Final Real-time Localization
DATE:    25/10/31 07:31:22 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 07:21:00 UT on 31 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251031A (trigger 783588065.486224 / 251031306).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 190.3, Dec = -17.6 (J2000 degrees, equivalent to J2000 12h 41m, -17d 36'), with a statistical uncertainty of 3.3 degrees.

The angle from the Fermi LAT boresight is 49.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251031306/quicklook/glg_skymap_all_bn251031306.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/bn251031306/quicklook/glg_healpix_all_bn251031306.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251031306/quicklook/glg_lc_medres34_bn251031306.gif