GCN Circular 41517
Subject
GRB 250823A: Fermi GBM Observation
Event
Date
2025-08-24T02:09:14Z (a month ago)
From
Jacob Smith at Fermi-GBM Team <jrs0118@uah.edu>
Via
Web form
Jacob Smith (UAH), B. Mailyan (Florida Tech) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
At 20:10:10.67 UT on 23 August 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250823A (trigger 777672615/250823840),
which was also detected by Swift BAT (M. H. Siegel et al. 2025, GCN 41511),
and optical follow-up was first reported by Liverpool Telescope (B. P. Gompertz et al. 2025, GCN 41512).
The Fermi GBM on-ground location is consistent with the Swift BAT position.
The angle from the Fermi LAT boresight is 72 degrees.
The GBM light curve consists of a single emission episode with a duration (T90)
of about 13 s (50-300 keV). The time-averaged spectrum
from T0-6.1 to T0+10.2 s is best fit by
a simple power law function with index -1.67 +/- 0.05.
A power law function with an exponential high-energy cutoff fits equally well with power law index = -1.44 +/- 0.17 and Epeak = 206.5 +/- 95.8.
The event fluence (10-1000 keV) in this time interval is
(1.9 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.1 s in the 10-1000 keV band is 1.8 +/- 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/