TITLE:   GCN CIRCULAR
NUMBER:  42028
SUBJECT: GRB 250929A: Fermi GBM Final Real-time Localization
DATE:    25/09/29 20:16:36 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 20:06:07 UT on 29 Sep 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250929A (trigger 780869172.178268 / 250929838).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 58.2, Dec = -60.2 (J2000 degrees, equivalent to J2000 03h 52m, -60d 12'), with a statistical uncertainty of 11.5 degrees.

The angle from the Fermi LAT boresight is 73.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250929838/quicklook/glg_skymap_all_bn250929838.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/bn250929838/quicklook/glg_healpix_all_bn250929838.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250929838/quicklook/glg_lc_medres34_bn250929838.gif