GCN Circular 23183
Subject
GRB 180828A: Fermi GBM observation
Date
2018-08-29T04:19:38Z (6 years ago)
From
Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>
O.J. Roberts (USRA/NASA) and C. Meegan (UAH) report on behalf
of the Fermi GBM Team:
"At 18:57:26.58 UT on 28 August 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180828A (trigger 557175451 / 180828790),
which was also detected by Swift (Beardmore et al. 2018, GCN 23182).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time using the
Swift-XRT position is 77 degrees.
The GBM light curve consists of multiple bright pulses with a duration
(T90) of 8.3 s (50-300 keV). The time-averaged spectrum from T0+1.5s to
T0+11 s is best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.46 +/- 0.02 and the
cutoff energy, parameterized as Epeak, is 358 +/- 9 keV.
A Band function fits the interval equally well, with
Epeak =346 +/- 12 keV, alpha = -0.44 +/- 0.03 and
beta = -3.01 +/- 0.33.
The event fluence (10-1000 keV) over the T90 interval is
(3.39 +/- 0.5)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0 +8s in the 10-1000 keV band is 38 +/- 1 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."