TITLE:   GCN CIRCULAR
NUMBER:  41839
SUBJECT: GRB 250916A: Fermi GBM Final Real-time Localization
DATE:    25/09/16 13:40:16 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 13:29:21 UT on 16 Sep 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250916A (trigger 779722166.007904 / 250916562).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 29.3, Dec = 40.3 (J2000 degrees, equivalent to J2000 01h 57m, 40d 17'), with a statistical uncertainty of 9.8 degrees.

The angle from the Fermi LAT boresight is 66.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250916562/quicklook/glg_skymap_all_bn250916562.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/bn250916562/quicklook/glg_healpix_all_bn250916562.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250916562/quicklook/glg_lc_medres34_bn250916562.gif