GCN 43800: GRB 260221B: Fermi GBM Final Real-time Localization

2026-02-21T23:29:14.552Z | rev 0 | event: GRB 260221B

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

At 23:18:22 UT on 21 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260221B (trigger 793408707.776836 / 260221971).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 328.4, Dec = 75.0 (J2000 degrees, equivalent to J2000 21h 53m, 75d 00'), with a statistical uncertainty of 8.4 degrees.

The angle from the Fermi LAT boresight is 12.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260221971/quicklook/glg_skymap_all_bn260221971.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/bn260221971/quicklook/glg_healpix_all_bn260221971.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260221971/quicklook/glg_lc_medres34_bn260221971.gif