TITLE:   GCN CIRCULAR
NUMBER:  39688
SUBJECT: GRB 250302A: Fermi GBM Observation
DATE:    25/03/12 17:18:02 GMT
FROM:    Marianna Dafčíková at Masaryk University <500025@mail.muni.cz>

M. Dafcikova (MUNI) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 13:46:32.99 UT on 02 March 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250302A (trigger 762615997/250302574).
which was also detected by Swift/BAT-GUANO (DeLaunay et al. 2025, GCN 39675).
The Fermi GBM on-ground location is consistent with the Swift/BAT position.

The angle from the Fermi LAT boresight is 67 degrees.

The GBM light curve consists of multiple peaks with a duration (T90)
of about 56 s (50-300 keV). The time-averaged spectrum
from T0-3.6 to T0+71.2 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.49 +/- 0.06 and the cutoff energy,
parameterized as Epeak, is 394 +/- 135 keV.

The event fluence (10-1000 keV) in this time interval is
(8.8 +/- 0.5)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+10 s in the 10-1000 keV band is 2.5 +/- 0.2 ph/s/cm^2.

A Band function fits the spectrum equally well with Epeak = 324 +/- 194
keV, alpha = -1.48 +/- 0.09 and beta = -2.0 +/- 0.3.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"