TITLE:   GCN CIRCULAR
NUMBER:  44979
SUBJECT: GRB 260618B: Fermi GBM Final Real-time Localization
DATE:    26/06/18 17:07:30 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 16:55:04 UT on 18 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260618B (trigger 803494509.712104 / 260618705).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 351.1, Dec = -44.1 (J2000 degrees, equivalent to J2000 23h 24m, -44d 06'), with a statistical uncertainty of 1.8 degrees.

The angle from the Fermi LAT boresight is 18.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260618705/quicklook/glg_skymap_all_bn260618705.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/bn260618705/quicklook/glg_healpix_all_bn260618705.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260618705/quicklook/glg_lc_medres34_bn260618705.gif