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GCN Circular 19312

Subject
Konus-Wind observation of GRB 160409A
Date
2016-04-13T13:13:04Z (8 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov,
D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:

The long-duration GRB 160409A (Swift-BAT ground detection:
Evans et al., GCN 19304) triggered Konus-Wind
at T0=21254.430 s UT (05:54:14.430).

The KW light curve shows single structure-less pulse with
a total duration of ~35 s.
The emission is visible up to ~7 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160409_T21254/

As observed by Konus-Wind, the burst had a fluence
of 1.8(-0.3,+0.3)x10^-5 erg/cm2, and a 64-ms peak flux,
measured from T0+4.846 s, of 1.5(-0.2,+0.2)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+24.832 s)
is best fit in the 20 keV - 15 MeV range
by the cutoff power law with the following model parameters:
the photon index alpha = -0.68(-0.16,+0.18),
and the peak energy Ep = 209(-18,+22) keV,
chi2 = 107/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep with an upper limit on beta of -2.1

The spectrum near the peak count rate (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range
by the cutoff power law with the following model parameters:
the photon index alpha = -0.72(-0.17,+0.19),
and the peak energy Ep = 252(-26,+32) keV,
chi2 = 122/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep with an upper limit on beta of -2.0

All the quoted errors are at the 1 sigma confidence level.
All the quoted values are preliminary.
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