TITLE:   GCN CIRCULAR
NUMBER:  39623
SUBJECT: GRB 250309A: Fermi GBM Final Real-time Localization
DATE:    25/03/09 00:53:02 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 SHORT GRB

At 00:42:03 UT on 9 Mar 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250309A (trigger 763173728.785018 / 250309029).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 46.7, Dec = 58.0 (J2000 degrees, equivalent to J2000 03h 06m, 58d 00'), with a statistical uncertainty of 22.9 degrees.

The angle from the Fermi LAT boresight is 22.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309029/quicklook/glg_skymap_all_bn250309029.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/bn250309029/quicklook/glg_healpix_all_bn250309029.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309029/quicklook/glg_lc_medres34_bn250309029.gif