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GCN Circular 23666

GRB 190109B: Fermi GBM observation
2019-01-09T23:30:49Z (5 years ago)
Cori Fletcher at USRA/NASA <>
C. Fletcher (USRA) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 11:56:10.76 UT on 09 January 2019, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 190109B (trigger 568727775 / 190109497)
which was also detected by the Swift (Sbarufatti et al. 2019, GCN 23648).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 46 degrees.

The GBM light curve consists of a single peak
with a duration (T90) of about 8 s (50-300 keV).
The time-averaged spectrum from T0-6.1 s to T0+3.1 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.85 +/- 0.25 and
the cutoff energy, parameterized as Epeak, is 92 +/- 14 keV.

The event fluence (10-1000 keV) in this time interval is
(6.76 +/- 0.67)E-7 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-1.6 s in the 10-1000 keV band
is 2.8 +/- 0.2 ph/s/cm^2.

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