GCN Circular 38844

O. Mukherjee (USRA), A. Myers (NPP/GSFC) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 05:02:30.29 UT on 07 January 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250107A (trigger 757918955/250107210).
which was also detected by Swift/BAT-GUANO (DeLaunay et al. 2025, GCN 38840
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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 21 degrees.

The GBM light curve consists of a single emission episode with multiple peaks with a duration (T90)
of about 53 s (50-300 keV). The time-averaged spectrum
from T0-2.8 to T0+35.1 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.22 +/- 0.06 and the cutoff energy,
parameterized as Epeak, is 390 +/- 80 keV.

The event fluence (10-1000 keV) in this time interval is
(7.8 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+6.85 s in the 10-1000 keV band is 3.6 +/- 0.24 ph/s/cm^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/"