TITLE:   GCN CIRCULAR
NUMBER:  45710
SUBJECT: GRB 260923A: Fermi GBM Final Real-time Localization
DATE:    26/09/23 23:52:10 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 23:41:36 UT on 23 Sep 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260923A (trigger 811899701.42774 / 260923987).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 345.9, Dec = -54.1 (J2000 degrees, equivalent to J2000 23h 03m, -54d 06'), with a statistical uncertainty of 2.1 degrees.

The angle from the Fermi LAT boresight is 30.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260923987/quicklook/glg_skymap_all_bn260923987.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/bn260923987/quicklook/glg_healpix_all_bn260923987.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260923987/quicklook/glg_lc_medres34_bn260923987.gif