GCN Circular 41828

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

"At 21:06:23.64 UT on 12 September 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250912A (trigger 779403988/250912879),
which was also detected by SVOM/ECLAIRs (Jean-Grégoire Ducoin et al. 2025, GCN 41820
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 ).
The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position.

The angle from the Fermi LAT boresight is 49 degrees.

The GBM light curve consists of multiple emission episodes with a duration (T90)
of about 15 s (50-300 keV). The time-averaged spectrum
from T0 to T0+15.6 s is best fit by
a simple power law function with index -1.31 +/- 0.04.
A power law function with an exponential high-energy cutoff 
fits the spectrum equally well with a with power law index = -1.05 +/- 0.12 and Epeak = 783 +/- 359.

The event fluence (10-1000 keV) in this time interval is
(3.1 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.26 s in the 10-1000 keV band is 4 +/- 0.2 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/"