TITLE:   GCN CIRCULAR
NUMBER:  43957
SUBJECT: GRB 260311A: Fermi GBM Final Real-time Localization
DATE:    26/03/11 03:46:15 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 SHORT GRB

At 03:35:40 UT on 11 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260311A (trigger 794892945.615954 / 260311150).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 291.3, Dec = -43.5 (J2000 degrees, equivalent to J2000 19h 25m, -43d 30'), with a statistical uncertainty of 10.8 degrees.

The angle from the Fermi LAT boresight is 111.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260311150/quicklook/glg_skymap_all_bn260311150.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/bn260311150/quicklook/glg_healpix_all_bn260311150.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260311150/quicklook/glg_lc_medres34_bn260311150.gif