GCN Circular 45685

The Fermi GBM team reports the detection of a likely LONG GRB

"At 21:44:37.15 UT on 21 September 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260921B (trigger 811719882/260921906).

The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 62.12, Dec = 31.21 (J2000 degrees, equivalent to J2000 4h 8m, +31d 12'),
with a statistical uncertainty of 2.22 degrees.

The angle from the Fermi LAT boresight is 107 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260921906/quicklook/glg_skymap_all_bn260921906.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/bn260921906/quicklook/glg_healpix_all_bn260921906.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260921906/quicklook/glg_lc_medres34_bn260921906.gif"