TITLE:   GCN CIRCULAR
NUMBER:  39618
SUBJECT: GRB 250307A: Fermi GBM Final Real-time Localization
DATE:    25/03/07 20:08:14 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 19:57:53 UT on 7 Mar 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250307A (trigger 763070278.733804 / 250307832).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 265.6, Dec = 2.2 (J2000 degrees, equivalent to J2000 17h 42m, 2d 12'), with a statistical uncertainty of 2.7 degrees.

The angle from the Fermi LAT boresight is 82.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250307832/quicklook/glg_skymap_all_bn250307832.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/bn250307832/quicklook/glg_healpix_all_bn250307832.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250307832/quicklook/glg_lc_medres34_bn250307832.gif