GCN Circular 43139
Subject
GRB 251216A: Fermi GBM Final Real-time Localization
Event
Date
2025-12-16T09:48:49Z (2 days ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
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