TITLE:   GCN CIRCULAR
NUMBER:  41660
SUBJECT: GRB 250902B: Fermi GBM Final Real-time Localization
DATE:    25/09/02 18:56:35 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 18:45:34 UT on 2 Sep 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250902B (trigger 778531539.099344 / 250902782).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 82.3, Dec = -5.0 (J2000 degrees, equivalent to J2000 05h 29m, -5d 00'), with a statistical uncertainty of 1.4 degrees.

The angle from the Fermi LAT boresight is 20.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250902782/quicklook/glg_skymap_all_bn250902782.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/bn250902782/quicklook/glg_healpix_all_bn250902782.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250902782/quicklook/glg_lc_medres34_bn250902782.gif