GCN Circular 42582
Subject
GRB 251103B: Fermi GBM observation
Event
Date
2025-11-04T21:18:14Z (2 days ago)
Edited On
2025-11-05T23:29:29Z (16 hours ago)
From
atrigg2@lsu.edu
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of atrigg2@lsu.edu
Via
Web form
A. C. Trigg (NPP, NASA MSFC)
report on behalf of the Fermi GBM Team:
"At 16:46:36.44 UT on 03 November 2025, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 251103B (trigger 783881201/251103699),
which was also detected by the Swift/XRT (Evans et al. 2025, GCN 42557)
The Fermi GBM Final Real-time Localization (GCN 42555) is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 70 degrees.
The GBM light curve shows/consists of rapid multi-peaked emission
with a duration (T90) of about 48 s (50-300 keV).
The time-averaged spectrum from T0-16.1 s to T0+39.8 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.36 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 82 +/- 2 keV.
The event fluence (10-1000 keV) in this time interval is
(4.67 +/- 0.12)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.98 s in the 10-1000 keV band
is 5 +/- 0.3 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/"