GCN 44751: GRB 260531C: Fermi GBM Final Localization Correction
2026-05-31T23:57:21.155Z | rev 0
The Fermi GBM team reports the detection of a likely SHORT GRB.
"At 21:14:58.91 UT on 31 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260531C (trigger 801954903/260531885). This trigger was initially classified as Below Horizon by the flight software, but is in fact a GRB.
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 40.6, Dec = 36.2 (J2000 degrees, equivalent to J2000 2h 42m, +36d 12'), with a statistical uncertainty of 11.6 degrees.
The angle from the Fermi LAT boresight is 82 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260531885/quicklook/glg_skymap_all_bn260531885.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/bn260531885/quicklook/glg_healpix_all_bn260531885.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260531885/quicklook/glg_lc_medres34_bn260531885.gif"