GCN Circular 43324
Subject
GRB 260104C: Fermi GBM Final Real-time Localization
Event
Date
2026-01-05T00:08:31Z (5 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 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