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GCN Circular 22588

Subject
Konus-Wind observation of GRB 180402A
Date
2018-04-03T16:59:32Z (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, hard-spectrum GRB 180402A
(Swift-BAT detection: Lien et al., GCN Circ. 22580;
Fermi-GBM detection: Malacaria, GCN Circ. 22585)
triggered Konus-Wind at T0=35100.353 s UT (09:45:00.353).

The burst light curve shows bright, multi-peaked emission episode,
which starts at T0-64 ms and has a total duration of ~180 ms,
preceded by a weaker pulse at ~T0-340 ms.

As observed by Konus-Wind, the burst
had a fluence of 2.14(-0.33,+0.53)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.086 s,
of 2.03(-0.45,+0.60)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

Since the most intense part of the burst was detected before
the trigger, the spectral analysis was performed using
the KW 3-channel light curve data.

Modeling the KW 3-channel spectrum of the main episode
(from T0-0.064 s to T0+0.116 s)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -0.01(-0.43,+0.64), and Ep = 703(-161,+276) keV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180402_T35100

All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.
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