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GCN Circular 23060

Subject
Konus-Wind observation of GRB 180728B
Date
2018-07-30T12:14:01Z (6 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks,
M. Ulanov, A. Tsvetkova, A. Lysenko, A.Kozlova, and T. Cline
on behalf of the Konus-Wind team, report:

The short-duration GRB 180728B
(IPN triangulation Svinkin et al., GCN Circ. 23056)
triggered Konus-Wind at T0=76197.29 s UT (21:09:57.290).

The burst light curve shows a multi-peaked structure
which starts at ~T0-0.2 s and has a total duration of ~0.4 s.
The emission is seen up to ~5 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180728_T76197/

As observed by Konus-Wind, the burst
had a fluence of 1.35(-0.22,+0.25)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0-0.004 s,
of 9.59(-3.38,+3.55)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+0.192 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = 0.25(-0.61,+0.88)
and Ep = 404(-74,+118) keV (chi2 = 15/17 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.2
(chi2 = 15/16 dof).

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