TITLE:   GCN CIRCULAR
NUMBER:  42093
SUBJECT: GRB 251002A: Fermi GBM Observation
DATE:    25/10/03 14:21:41 GMT
FROM:    Jacob Smith at Fermi-GBM Team <jrs0118@uah.edu>

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

"At 20:14:51.01 UT on 02 October 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 251002A (trigger 781128896/251002844).
which was also detected by SVOM/ECLAIRs (A. Saccardi et al. 2025, GCN 42060).
The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position.
VLT/X-shooter detected a spectroscopic redshift of z = 2.178 (A. Saccardi et al. 2025, GCN 42076).

The angle from the Fermi LAT boresight is 53 degrees.

The GBM light curve multiple emission episodes with a duration (T90)
of about 26 s (50-300 keV). The time-averaged spectrum
from T0-6.9 to T0+14.6 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.88 +/- 0.07 and the cutoff energy,
parameterized as Epeak, is 180 +/- 10 keV.

The event fluence (10-1000 keV) in this time interval is
(4.6 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+7.9 s in the 10-1000 keV band is 7.1 +/- 0.2 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 140 +/- 20 keV, alpha = -0.7 +/- 0.1 and beta = -2.2 +/- 0.1.

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/"