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GCN Circular 21857

Subject
Konus-Wind observation of GRB 170906C
Date
2017-09-11T15:53:01Z (7 years ago)
From
Anastasia Tsvetkova at Ioffe Institute <tsvetkova@mail.ioffe.ru>
A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik,
M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 170906C (Swift-BAT trigger #770981:
Siegel et al., GCN 21826; Lien et al., GCN 21832)
triggered Konus-Wind at T0=26780.985 s UT (07:26:20.985).

The burst light curve shows a single pulse
started at ~T0-40.8 s with a total duration of ~65.8 s.
The emission is seen up to ~4 MeV.

As observed by Konus-Wind, the burst
had a fluence of�� 1.60(-0.19,+0.28)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+0.354 s,
of 2.77(-0.73,+0.74)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 4 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with�� alpha = -1.06(-0.18,+0.19),
and Ep = 154(-19,+26) keV (chi2 = 64/72 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.56 (chi2 = 64/71 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170906_T26780/

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
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