TITLE:   GCN CIRCULAR
NUMBER:  43246
SUBJECT: GRB 251228A: Fermi GBM Final Real-time Localization
DATE:    25/12/28 00:52:53 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 SHORT GRB

At 00:42:10 UT on 28 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251228A (trigger 788575335.25706 / 251228029).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 150.2, Dec = 49.8 (J2000 degrees, equivalent to J2000 10h 00m, 49d 47'), with a statistical uncertainty of 10.7 degrees.

The angle from the Fermi LAT boresight is 107.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251228029/quicklook/glg_skymap_all_bn251228029.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/bn251228029/quicklook/glg_healpix_all_bn251228029.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251228029/quicklook/glg_lc_medres34_bn251228029.gif