GCN Circular 32866
Subject
GRB 221027A: Fermi GBM detection
Date
2022-10-27T14:45:08Z (2 years ago)
From
Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>
O.J. Roberts (USRA/NASA-MSFC) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 04:09:34.35 UT on 27 October 2022, the Fermi
Gamma-Ray Burst Monitor (GBM) triggered and located
GRB 221027A (trigger 688536579 / 221027173), which was
also detected by Fermi-LAT (M. Arimoto et al. 2022, GCN 32862).
The Fermi GBM Final Real-time Localization (GCN 32861) is
consistent with the LAT position.
The angle from the Fermi LAT boresight at the GBM trigger
time is 51 degrees.
The GBM light curve consists of a bright pulse
with a duration (T90) of about 7 s (50-300 keV).
The time-averaged spectrum from T0-1.5s to T0+9.7 s is
best fit by a Band function with Epeak = 341 +/- 37 keV,
alpha = -0.75 +/- 0.06, and beta = -2.09 +/- 0.14.
The event fluence (10-1000 keV) in this time interval is
(9.2 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux
measured starting from T0+1.2 s in the 10-1000 keV band
is 8.5 +/- 0.3 ph/s/cm^2.
A power law function with an exponential high-energy cutoff
fits the spectrum equally well. The power law index
is -0.81 +/- 0.04 and the cutoff energy, parameterized as
Epeak, is 411 +/- 29 keV
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/"