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GCN Circular 21085

GRB 170510A: Fermi GBM observation
2017-05-10T17:47:13Z (7 years ago)
Oliver J Roberts at USRA/NASA <>
O.J. Roberts (USRA/NASA), E. Bissaldi (Politecnico & INFN Bari)  
and C. Meegan (UAH) report on behalf of the Fermi GBM Team:

"At 05:12:25.73 UT on 10 May 2017, the Fermi Gamma-Ray Burst 
Monitor triggered and located GRB 170510A 
(trigger 516085950 / 170510217), which was also detected by the 
Fermi/LAT (Bissaldi et al. 2017, GCN 21081).

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 angle from the Fermi LAT boresight is 67 degrees.

The GBM light curve consists of multiple peaks with a 
duration (T90) of about 128 s (50-300 keV). The time-averaged
spectrum from T0+2.0 s to T0+130.0 s is best fit by a power law
function with an exponential high-energy cutoff. The power law 
index is -0.82 +/- 0.03 and the cutoff energy, parameterized as 
Epeak, is 302 +/- 13 keV.

A Band function fits the spectrum equally well with 
Epeak= 264 +/- 17 keV, alpha = -0.77 +/- 0.04 and 
beta = -2.33 +/- 0.16.

The event fluence (10-1000 keV) in this time interval is
(4.78 +/- 0.11)E-05 erg/cm^2. The 1-sec peak photon flux 
measured starting from T0+21.8 s in the 10-1000 keV band 
is 17.0 +/- 0.4 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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