TITLE:   GCN CIRCULAR
NUMBER:  42555
SUBJECT: GRB 251103B: Fermi GBM Final Real-time Localization
DATE:    25/11/03 16:57:10 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 16:46:36 UT on 3 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251103B (trigger 783881201.440798 / 251103699).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 107.5, Dec = -22.0 (J2000 degrees, equivalent to J2000 07h 10m, -22d 00'), with a statistical uncertainty of 4.3 degrees.

The angle from the Fermi LAT boresight is 67.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251103699/quicklook/glg_skymap_all_bn251103699.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/bn251103699/quicklook/glg_healpix_all_bn251103699.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251103699/quicklook/glg_lc_medres34_bn251103699.gif