TITLE:   GCN CIRCULAR
NUMBER:  43955
SUBJECT: GRB 260310B: Fermi GBM Final Real-time Localization
DATE:    26/03/10 21:49:02 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 21:41:23 UT on 10 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260310B (trigger 794871688.893658 / 260310904).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 119.6, Dec = 12.9 (J2000 degrees, equivalent to J2000 07h 58m, 12d 54'), with a statistical uncertainty of 6.7 degrees.

The angle from the Fermi LAT boresight is 68.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260310904/quicklook/glg_skymap_all_bn260310904.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/bn260310904/quicklook/glg_healpix_all_bn260310904.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260310904/quicklook/glg_lc_medres34_bn260310904.gif