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GCN Circular 34750

Subject
GRB 230919A: Fermi GBM Observation
Date
2023-09-20T20:49:41Z (3 months ago)
From
Lorenzo Scotton at UAH <lscottongcn@outlook.com>
Via
Web form
L. Scotton (UAH), C. Fletcher (USRA) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 16:58:23.86 UT on 19 September 2023, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 230919A (trigger 716835508/230919707).
which was also detected by AstroSat (Navaneeth et al. 2023, GCN 34742)
and Swift/BAT-GUANO (DeLaunay et al. 2023, GCN 34747).

The Fermi GBM Final Real-time Localization was reported in GCN 34737.

The angle from the Fermi LAT boresight is 120 degrees.

The GBM light curve consists of multiple peaks 
with a duration (T90) of about 2.9s. The time-averaged spectrum
from T0-0.06 to T0+1.34 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.74 +/- 0.06 and the cutoff energy,
parameterized as Epeak, is 2023 +/- 271 keV. 
A Band function fits the spectrum equally well with
Epeak = 1617 +/- 352 keV, alpha = -0.68 +/- 0.08 and beta = -2.43 +/- 0.32.

The event fluence (10-1000 keV) in this time interval is
(3.3 +/- 0.1)E-06 erg/cm^2. The 64-msec peak photon flux measured
starting from T0+0.58 s in the 10-1000 keV band is 12 +/- 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/"
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