TITLE:   GCN CIRCULAR
NUMBER:  44340
SUBJECT: GRB 260418B: Fermi GBM Final Real-time Localization
DATE:    26/04/18 16:30:58 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 16:20:21 UT on 18 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260418B (trigger 798222026.725586 / 260418681).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 34.7, Dec = -40.5 (J2000 degrees, equivalent to J2000 02h 18m, -40d 30'), with a statistical uncertainty of 4.0 degrees.

The angle from the Fermi LAT boresight is 47.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260418681/quicklook/glg_skymap_all_bn260418681.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/bn260418681/quicklook/glg_healpix_all_bn260418681.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260418681/quicklook/glg_lc_medres34_bn260418681.gif