GCN Circular 22597
Subject
GRB 180404B: Fermi GBM observation
Date
2018-04-04T10:04:46Z (6 years ago)
From
Andreas von Kienlin at MPE <azk@mpe.mpg.de>
A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team:
"At 02:11:38.64 UT on 04 April 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180404B (trigger 544500703 / 180404091),
which was also detected by the Swift/BAT (LaPorte et al. 2018, GCN 22590).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 61.3 degrees.
The GBM light curve shows a single bright peak followed by
a secondary emission episode with a duration (T90) of about 80 s (50-300 keV).
The time-averaged spectrum from T0+0.003 s to T0+33.281 s is well fit by
a power law function with an exponential
high-energy cutoff. The power law index is -0.40 +/- 0.04 and
the cutoff energy, parameterized as Epeak, is 209 +/- 6 keV.
The event fluence (10-1000 keV) in this time interval is
(3.3 +/- 0.4)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+12.86 s in the 10-1000 keV band
is 8.0 +/- 0.3 ph/s/cm^2.
A Band function fits the spectrum equally well
with Epeak= 204 +/- 8 keV, alpha = -0.38 +/- 0.04 and beta = -3.3 +/- 0.6.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."