TITLE:   GCN CIRCULAR
NUMBER:  43920
SUBJECT: GRB 260305A: Fermi GBM Final Real-time Localization
DATE:    26/03/05 02:52:09 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 02:41:38 UT on 5 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260305A (trigger 794371303.18619 / 260305112).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 216.5, Dec = 34.0 (J2000 degrees, equivalent to J2000 14h 26m, 34d 00'), with a statistical uncertainty of 2.4 degrees.

The angle from the Fermi LAT boresight is 49.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260305112/quicklook/glg_skymap_all_bn260305112.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/bn260305112/quicklook/glg_healpix_all_bn260305112.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260305112/quicklook/glg_lc_medres34_bn260305112.gif