GCN Circular 20986
Subject
GRB 170405A: Fermi GBM observation
Date
2017-04-05T22:51:57Z (7 years ago)
From
C. Michelle Hui at MSFC/Fermi-GBM <c.m.hui@nasa.gov>
C. M. Hui (MSFC) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
At 18:39:22.89 UT on 05 April 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170405A (trigger 513110367/170405777),
which was also detected by Swift (Troja et al. 2017, GCN 20984).
The GBM on-ground location is consistent with the Swift position.
The trigger resulted in an Autonomous Repoint Request (ARR)
by the GBM Flight Software owing to the high peak flux of the GRB.
This ARR was accepted and the spacecraft slewed to the GBM in-flight
location. The initial angle from the Fermi LAT boresight is 52 degrees.
The GBM light curve shows multiple peaks
with a duration (T90) of about 78.6 s (50-300 keV).
The time-averaged spectrum from T0+7.2 s to T0+86.0 s is
adequately fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.01 +/- 0.01 and
the cutoff energy, parameterized as Epeak, is 355.2 +/- 8.6 keV.
The event fluence (10-1000 keV) in this time interval is
(7.85 +/- 0.07)E-05 erg/cm^2. The 1s peak photon flux measured
starting from T0+29.5 s in the 10-1000 keV band is
15.8 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog.