TITLE:   GCN CIRCULAR
NUMBER:  39635
SUBJECT: GRB 250309B: Fermi GBM Final Localization
DATE:    25/03/09 15:47:40 GMT
FROM:    Padraig McDermott at University College Dublin <padraig.mcdermott@ucdconnect.ie>

The Fermi GBM team reports the detection of a likely LONG GRB

"At 07:38:30.66 UT on 09 March 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250309B (trigger 763198715/250309318).

The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 210.58, Dec = -10.86 (J2000 degrees, equivalent to J2000 14h 02m, -10d 51'),
with a statistical uncertainty of 1.2 degrees.

The angle from the Fermi LAT boresight is 77 degrees.

The skymap can be found here:
http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309318/quicklook/glg_skymap_all_bn250309318.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309318/quicklook/glg_healpix_all_bn250309318.fit

The GBM light curve can be found here:
http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309318/quicklook/glg_lc_medres34_bn250309318.gif"