TITLE:   GCN CIRCULAR
NUMBER:  45973
SUBJECT: GRB 261017A: Fermi GBM Final Real-time Localization
DATE:    26/10/17 16:15:32 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 16:05:05 UT on 17 Oct 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 261017A (trigger 813945910.098688 / 261017670).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 141.9, Dec = 14.8 (J2000 degrees, equivalent to J2000 09h 27m, 14d 48'), with a statistical uncertainty of 2.4 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/bn261017670/quicklook/glg_skymap_all_bn261017670.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/bn261017670/quicklook/glg_healpix_all_bn261017670.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261017670/quicklook/glg_lc_medres34_bn261017670.gif