TITLE:   GCN CIRCULAR
NUMBER:  43139
SUBJECT: GRB 251216A: Fermi GBM Final Real-time Localization
DATE:    25/12/16 09:48:49 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 09:38:09 UT on 16 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251216A (trigger 787570694.65431 / 251216401).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 290.9, Dec = 52.0 (J2000 degrees, equivalent to J2000 19h 23m, 52d 00'), with a statistical uncertainty of 9.3 degrees.

The angle from the Fermi LAT boresight is 42.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251216401/quicklook/glg_skymap_all_bn251216401.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/bn251216401/quicklook/glg_healpix_all_bn251216401.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251216401/quicklook/glg_lc_medres34_bn251216401.gif