TITLE:   GCN CIRCULAR
NUMBER:  44808
SUBJECT: GRB 260603B: Fermi GBM Final Localization
DATE:    26/06/03 18:16:31 GMT
FROM:    Eva M. Palafox at INAOE <eva.palafox@gmail.com>

The Fermi GBM team reports the detection of a likely LONG GRB

"At 16:44:46.61 UT on 03 June 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260603B (trigger 802197891/260603698).

The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 350.27, Dec = 39.20 (J2000 degrees, equivalent to J2000 +23h 21m, +39d 12'),
with a statistical uncertainty of 3.16 degrees.

The angle from the Fermi LAT boresight is 63 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260603698/quicklook/glg_skymap_all_bn260603698.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/bn260603698/quicklook/glg_healpix_all_bn260603698.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260603698/quicklook/glg_lc_medres34_bn260603698.gif"