TITLE:   GCN CIRCULAR
NUMBER:  44648
SUBJECT: GRB 260516C: Fermi GBM Final Real-time Localization
DATE:    26/05/16 19:45:10 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 19:34:38 UT on 16 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260516C (trigger 800652883.931176 / 260516816).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 172.6, Dec = -59.9 (J2000 degrees, equivalent to J2000 11h 30m, -59d 53'), with a statistical uncertainty of 3.2 degrees.

The angle from the Fermi LAT boresight is 36.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260516816/quicklook/glg_skymap_all_bn260516816.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/bn260516816/quicklook/glg_healpix_all_bn260516816.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260516816/quicklook/glg_lc_medres34_bn260516816.gif