TITLE:   GCN CIRCULAR
NUMBER:  44553
SUBJECT: GRB 260511C: Fermi GBM Final Real-time Localization
DATE:    26/05/11 15:26:25 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 15:15:49 UT on 11 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260511C (trigger 800205354.688558 / 260511636).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 219.4, Dec = 39.3 (J2000 degrees, equivalent to J2000 14h 37m, 39d 17'), with a statistical uncertainty of 14.9 degrees.

The angle from the Fermi LAT boresight is 50.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260511636/quicklook/glg_skymap_all_bn260511636.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/bn260511636/quicklook/glg_healpix_all_bn260511636.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260511636/quicklook/glg_lc_medres34_bn260511636.gif