TITLE:   GCN CIRCULAR
NUMBER:  45473
SUBJECT: GRB 260831A: Fermi GBM Final Real-time Localization
DATE:    26/08/31 04:17:21 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>

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

At 04:09:00 UT on 31 Aug 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260831A (trigger 809842145.925584 / 260831173).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 220.0, Dec = -7.2 (J2000 degrees, equivalent to J2000 14h 39m, -7d 12'), with a statistical uncertainty of 6.5 degrees.

The angle from the Fermi LAT boresight is 84.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260831173/quicklook/glg_skymap_all_bn260831173.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/bn260831173/quicklook/glg_healpix_all_bn260831173.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260831173/quicklook/glg_lc_medres34_bn260831173.gif