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GCN Circular 21005

GRB 170409A: Fermi GBM Observation
2017-04-09T17:34:02Z (7 years ago)
Eric Burns at U of Alabama <>
E. Burns (UAH), E. Bissaldi (Politecnico & INFN Bari),
S. Poolakkil (UAH), and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 02:42:00.49 UT on 09 April 2017 , the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170409A (trigger 513398525/170409113)
which was also detected by the Fermi LAT (Longo et al. 2017, GCN 21004).
The GBM on-ground location is consistent with the LAT 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 to
the LAT location is 82 degrees.

The GBM light curve shows multiple peaks
with a duration (T90) of about 68 s (50-300 keV).
The time-averaged spectrum from T0+26.880 s to T0+97.537 s is
best fit by a Band function with Epeak = 1150 +/- 20 keV,
alpha = -0.82 +/- 0.01, and beta = -2.84 +/- 0.06.

The event fluence (10-1000 keV) in this time interval is
(2.956 +/- 0.009)E-04 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+38.0164 s in the 10-1000 keV band
is 61.8 +/- 0.6 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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