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GCN Circular 34830

GRB 231017A: Fermi GBM Detection
2023-10-18T16:19:02Z (8 months ago)
Joe Mangan at IJCLab <>
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J.Mangan (CNRS/IJCLab), E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 08:05:03.30 UT on 17 October 2023, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 231017A (trigger 719222708/231017337), which was also 
detected by the Swift/BAT-GUANO (DeLaunay et al. 2023, GCN 34824). 

The Fermi GBM Final Real-time Localization is reported in GCN 34822.

The GBM light curve consists of a single emission episode with a duration (T90)
of about 4.8 s (50-300 keV). The time-averaged spectrum
from T0-3.5 to T0+4.7 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.1 +/- 0.2 and the cutoff energy,
parameterized as Epeak, is 270 +/- 82 keV.

A Band function fits the spectrum equally well
with Epeak= 175 +/- 92 keV, alpha = -0.9 +/- 0.3 and beta = -1.9 +/- 0.3.

The event fluence (10-1000 keV) in this time interval is
(1.7 +/- 0.2)E-06 erg/cm^2. The 64-msec peak photon flux measured
starting from T0+0.77 s in the 10-1000 keV band is 7.8 +/- 1.6 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:"
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