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GCN Circular 26116

Subject
GRB 191031A: Fermi GBM detection
Date
2019-10-31T23:56:09Z (5 years ago)
From
Rachel Hamburg at UAH <rkh0007@uah.edu>
S. Lesage (UAH), R. Hamburg (UAH), and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 00:36:35.61 UT on 31 October 2019, the Fermi Gamma-Ray Burst Monitor
(GBM)
triggered and located GRB 191031A (trigger 594175000 / 191031025)
which was also detected by the Swift/BAT (D'Ai et al. 2019, GCN 26101)
The Fermi GBM Final Real-time Localization (GCN 26102) is consistent with
the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 106
degrees.

The GBM light curve shows two pulses with a duration (T90) of about 200 s
(50-300 keV). The time-averaged spectrum of the first pulse from T0-10.24 s
to T0+10.24 s is best fit by a power law with an exponential
high-energy cutoff. The power law index is -0.9 +/- 0.2 and the cutoff
energy, parameterized as Epeak, is 218 +/- 57 keV. The time-averaged
spectrum of the second pulse from T+174.08 to T0+197.64 is best fit
by the same function with an index of -1.1 +/- 0.1 and an Epeak of 242 +/-
48 keV.

The event fluence (10-1000 keV) in the time interval of the two pulses is
(6.6 +/- 0.6)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+175.56 s in the 10-1000 keV band
is 2.5 +/- 0.3 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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