TITLE:   GCN CIRCULAR
NUMBER:  44193
SUBJECT: GRB 260402B: Fermi GBM Final Real-time Localization
DATE:    26/04/02 23:07:38 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 22:57:17 UT on 2 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260402B (trigger 796863442.54282 / 260402956).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 238.4, Dec = 0.2 (J2000 degrees, equivalent to J2000 15h 53m, 0d 12'), with a statistical uncertainty of 11.4 degrees.

The angle from the Fermi LAT boresight is 72.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260402956/quicklook/glg_skymap_all_bn260402956.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/bn260402956/quicklook/glg_healpix_all_bn260402956.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260402956/quicklook/glg_lc_medres34_bn260402956.gif