GCN 44747: GRB 260531B: Fermi GBM Final Real-time Localization

2026-05-31T14:08:37.965Z | rev 0 | event: GRB 260531B

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

At 13:57:59 UT on 31 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260531B (trigger 801928684.989378 / 260531582).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 282.6, Dec = 6.4 (J2000 degrees, equivalent to J2000 18h 50m, 6d 24'), with a statistical uncertainty of 2.2 degrees.

The angle from the Fermi LAT boresight is 48.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260531582/quicklook/glg_skymap_all_bn260531582.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/bn260531582/quicklook/glg_healpix_all_bn260531582.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260531582/quicklook/glg_lc_medres34_bn260531582.gif