TITLE:   GCN CIRCULAR
NUMBER:  41301
SUBJECT: GRB 250808A: Fermi GBM Observation
DATE:    25/08/09 12:34:41 GMT
FROM:    A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca@unitn.it>

A. Holzmann Airasca (UniTrento and INFN Bari), S. Bala (USRA) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 18:25:12.48 UT on 08 August 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250808A (trigger 776370317/250808768).
which was also detected by SVOM/ECLAIRs (D. Adrien et al. 2025, GCN 41297).
The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position.

The angle from the Fermi LAT boresight is 33 degrees.

The GBM light curve consists of a single variable emission episode with a duration (T90)
of about 49 s (50-300 keV). The time-averaged spectrum
from T0-6.1 to T0+51.2 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.1 +/- 0.2 and the cutoff energy,
parameterized as Epeak, is 70 +/- 7 keV.

The event fluence (10-1000 keV) in this time interval is
(2.7 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+45 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= 55 +/- 9 keV, alpha = -0.7 +/- 0.3 and beta = -2.5 +/- 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/"