TITLE:   GCN CIRCULAR
NUMBER:  44636
SUBJECT: GRB 260516B: Fermi GBM Final Real-time Localization
DATE:    26/05/16 05:23:15 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 05:12:36 UT on 16 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260516B (trigger 800601161.994496 / 260516217).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 161.5, Dec = 36.8 (J2000 degrees, equivalent to J2000 10h 46m, 36d 47'), with a statistical uncertainty of 4.8 degrees.

The angle from the Fermi LAT boresight is 58.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260516217/quicklook/glg_skymap_all_bn260516217.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/bn260516217/quicklook/glg_healpix_all_bn260516217.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260516217/quicklook/glg_lc_medres34_bn260516217.gif