TITLE:   GCN CIRCULAR
NUMBER:  46118
SUBJECT: GRB 261030B: Fermi GBM Final Real-time Localization
DATE:    26/10/30 21:54:00 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 21:43:27 UT on 30 Oct 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 261030B (trigger 815089412.659158 / 261030905).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 101.4, Dec = -52.8 (J2000 degrees, equivalent to J2000 06h 45m, -52d 47'), with a statistical uncertainty of 5.8 degrees.

The angle from the Fermi LAT boresight is 24.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261030905/quicklook/glg_skymap_all_bn261030905.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/bn261030905/quicklook/glg_healpix_all_bn261030905.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261030905/quicklook/glg_lc_medres34_bn261030905.gif