TITLE:   GCN CIRCULAR
NUMBER:  43324
SUBJECT: GRB 260104C: Fermi GBM Final Real-time Localization
DATE:    26/01/05 00:08:31 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 23:57:57 UT on 4 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260104C (trigger 789263882.41794 / 260104999).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 312.7, Dec = -26.1 (J2000 degrees, equivalent to J2000 20h 50m, -26d 06'), with a statistical uncertainty of 9.3 degrees.

The angle from the Fermi LAT boresight is 101.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260104999/quicklook/glg_skymap_all_bn260104999.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260104999/quicklook/glg_healpix_all_bn260104999.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260104999/quicklook/glg_lc_medres34_bn260104999.gif