TITLE:   GCN CIRCULAR
NUMBER:  42596
SUBJECT: GRB 251105A: Fermi GBM Observation
DATE:    25/11/05 23:37:24 GMT
FROM:    oindabimukherjee@gmail.com

O. Mukherjee (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 04:41:06.40 UT on 05 November 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 251105A (trigger 784010471/251105195)
which was also detected by Swift/BAT-GUANO (J. DeLaunay et al. 2025, GCN 42593).
The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position.

The angle from the Fermi LAT boresight is 41 degrees.

The GBM light curve consists of one emission episode with a duration (T90)
of about 65 s (50-300 keV). The time-averaged spectrum
from T0-23 to T0+87 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.13 +/- 0.06 and the cutoff energy,
parameterized as Epeak, is 220 +/- 30 keV.

A Band function fits the spectrum equally well
with Epeak= 190 +/- 30 keV, alpha = -1.08 +/- 0.08 and beta = -2.38 +/- 0.39.

The event fluence (10-1000 keV) in this time interval is
(1.26 +/- 0.07)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+8.8 s in the 10-1000 keV band is 3.2 +/- 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/"