TITLE:   GCN CIRCULAR
NUMBER:  43146
SUBJECT: GRB 251217A: Fermi GBM Final Real-time Localization
DATE:    25/12/17 04:46:13 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 04:35:34 UT on 17 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251217A (trigger 787638939.89203 / 251217191).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 325.8, Dec = 20.9 (J2000 degrees, equivalent to J2000 21h 43m, 20d 53'), with a statistical uncertainty of 6.6 degrees.

The angle from the Fermi LAT boresight is 29.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251217191/quicklook/glg_skymap_all_bn251217191.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/bn251217191/quicklook/glg_healpix_all_bn251217191.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251217191/quicklook/glg_lc_medres34_bn251217191.gif