TITLE:   GCN CIRCULAR
NUMBER:  42852
SUBJECT: GRB 251127A: Fermi GBM Final Real-time Localization
DATE:    25/11/27 03:28:10 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 03:17:42 UT on 27 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251127A (trigger 785906267.770746 / 251127137).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 155.6, Dec = 30.2 (J2000 degrees, equivalent to J2000 10h 22m, 30d 11'), with a statistical uncertainty of 4.1 degrees.

The angle from the Fermi LAT boresight is 24.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251127137/quicklook/glg_skymap_all_bn251127137.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/bn251127137/quicklook/glg_healpix_all_bn251127137.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251127137/quicklook/glg_lc_medres34_bn251127137.gif