TITLE:   GCN CIRCULAR
NUMBER:  43358
SUBJECT: GRB 260109B: Fermi GBM Final Real-time Localization
DATE:    26/01/09 08:52:04 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 08:41:22 UT on 9 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260109B (trigger 789640887.356258 / 260109362).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 197.5, Dec = -73.9 (J2000 degrees, equivalent to J2000 13h 09m, -73d 54'), with a statistical uncertainty of 13.7 degrees.

The angle from the Fermi LAT boresight is 54.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260109362/quicklook/glg_skymap_all_bn260109362.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/bn260109362/quicklook/glg_healpix_all_bn260109362.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260109362/quicklook/glg_lc_medres34_bn260109362.gif