GCN Circular 32556
Subject
GRB 220909A: Fermi GBM observation
Date
2022-09-14T13:30:13Z (3 years ago)
From
Christian Malacaria at ISSI <cmalacaria.astro@gmail.com>
C. Malacaria (ISSI) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 06:52:13.82 UT on 9 September 2022, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 220909A (trigger 684399138 / 220909286),
which was also detected by Swift/GUANO (Raman et al. 2022, GCN 32543).
The Fermi GBM Final Real-time Localization (GCN 32539) is consistent
with the Swift-BAT GUANO position.
The angle from the Fermi LAT boresight at the GBM trigger time is 46 degrees.
The GBM light curve shows a peak
with a duration (T90) of about 14.6 s (50-300 keV).
The time-averaged spectrum from T0-1.5 s to T0+6.7 s is
best fit by a power law function with an exponential
high-energy cutoff.
The power law index is -0.8 +/- 0.2 and
the cutoff energy, parameterized as Epeak, is 154 +/- 25 keV.
The event fluence (10-1000 keV) in this time interval is
(1.4 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.69 s in the 10-1000 keV band
is 3.6 +/- 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/"