TITLE:   GCN CIRCULAR
NUMBER:  46075
SUBJECT: GRB 261029B: Fermi GBM Final Real-time Localization
DATE:    26/10/29 02:34:51 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 02:24:10 UT on 29 Oct 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 261029B (trigger 814933455.723852 / 261029100).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 48.5, Dec = 4.3 (J2000 degrees, equivalent to J2000 03h 14m, 4d 17'), with a statistical uncertainty of 9.4 degrees.

The angle from the Fermi LAT boresight is 71.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261029100/quicklook/glg_skymap_all_bn261029100.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/bn261029100/quicklook/glg_healpix_all_bn261029100.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261029100/quicklook/glg_lc_medres34_bn261029100.gif