GCN Circular 39751

S. Bala (USRA) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 08:59:57.69 UT on 16 March 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250316A (trigger 763808402/250316375).
which was also detected by Swift/BAT-GUANO (Ronchini et al. 2025, GCN 39744
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 ).
The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position.

The angle from the Fermi LAT boresight is 98 degrees.

The GBM light curve consists of multiple peaks with a duration (T90)
of about 38.7 s (50-300 keV). The time-averaged spectrum
from T0-3.1 to T0+46.1 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.2 +/- 0.1 and the cutoff energy,
parameterized as Epeak, is 110 +/- 10 keV.

The event fluence (10-1000 keV) in this time interval is
(4.7 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+16 s in the 10-1000 keV band is 3.5 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 80 +/- 10 keV, alpha = -1 +/- 0.2 and beta = -2.3 +/- 0.2.

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/"