TITLE:   GCN CIRCULAR
NUMBER:  42342
SUBJECT: GRB 251018A: Fermi GBM Final Real-time Localization
DATE:    25/10/18 03:19:29 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 03:12:00 UT on 18 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251018A (trigger 782449925.633958 / 251018133).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 294.7, Dec = -40.3 (J2000 degrees, equivalent to J2000 19h 38m, -40d 17'), with a statistical uncertainty of 6.8 degrees.

The angle from the Fermi LAT boresight is 36.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251018133/quicklook/glg_skymap_all_bn251018133.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251018133/quicklook/glg_healpix_all_bn251018133.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251018133/quicklook/glg_lc_medres34_bn251018133.gif