TITLE:   GCN CIRCULAR
NUMBER:  41903
SUBJECT: GRB 250920C: Fermi GBM Final Real-time Localization
DATE:    25/09/20 15:36:01 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 15:25:17 UT on 20 Sep 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250920C (trigger 780074722.062672 / 250920643).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 47.6, Dec = -26.7 (J2000 degrees, equivalent to J2000 03h 10m, -26d 41'), with a statistical uncertainty of 1.2 degrees.

The angle from the Fermi LAT boresight is 93.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250920643/quicklook/glg_skymap_all_bn250920643.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/bn250920643/quicklook/glg_healpix_all_bn250920643.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250920643/quicklook/glg_lc_medres34_bn250920643.gif