TITLE:   GCN CIRCULAR
NUMBER:  45811
SUBJECT: GRB 261005A: Fermi GBM Final Real-time Localization
DATE:    26/10/05 20:29:41 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 20:19:03 UT on 5 Oct 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 261005A (trigger 812924348.321234 / 261005847).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 339.9, Dec = 5.5 (J2000 degrees, equivalent to J2000 22h 39m, 5d 30'), with a statistical uncertainty of 5.8 degrees.

The angle from the Fermi LAT boresight is 64.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261005847/quicklook/glg_skymap_all_bn261005847.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/bn261005847/quicklook/glg_healpix_all_bn261005847.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261005847/quicklook/glg_lc_medres34_bn261005847.gif