TITLE:   GCN CIRCULAR
NUMBER:  44249
SUBJECT: GRB 260409A: Fermi GBM Final Real-time Localization
DATE:    26/04/09 17:43:22 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 17:32:45 UT on 9 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260409A (trigger 797448770.671026 / 260409731).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 298.8, Dec = 61.6 (J2000 degrees, equivalent to J2000 19h 55m, 61d 36'), with a statistical uncertainty of 2.0 degrees.

The angle from the Fermi LAT boresight is 121.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260409731/quicklook/glg_skymap_all_bn260409731.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/bn260409731/quicklook/glg_healpix_all_bn260409731.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260409731/quicklook/glg_lc_medres34_bn260409731.gif