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GCN Circular 32204

Subject
Konus-Wind detection of an intermediate flare from SGR 1935+2154 on June 16
Date
2022-06-17T12:45:28Z (2 years ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
A.Ridnaia, D. Frederiks, A.Lysenko, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The bright burst from SGR 1935+2154
triggered Konus-Wind at T0=25915.887 s UT (07:11:55.887)
on 2022 June 16.

The light curve shows a single pulse with a sharp(<10 ms) rise
and a total duration of ~0.8 s.
The emission is seen up to ~200 keV.

The Konus-Wind light curve of this burst is available at
http://www.ioffe.ru/LEA/SGRs/220616_T25915/

As observed by Konus-Wind, the burst
had a fluence of 1.15(-0.03,+0.03)x10^-5 erg/cm2,
and a 16-ms peak flux, measured from T0+0.070 s,
of 2.32(-0.16,+0.16)x10^-5 erg/cm2/s
(both in the 20 - 500 keV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+0.256 s)
is best fit in the 20 - 500 keV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.35(-0.26,+0.28)
and Ep = 39(-2,+2) keV (chi2 = 17/22 dof).

The rather long duration of the burst along with the
large measured energy fluence put the burst in the class
of "intermediate" SGR bursts. Among 61 bright bursts
from SGR 1935+2154 detected by KW so far this event is
the fourth most fluent. The measured spectral
parameters are in typical range for bright short and
intermediate SGR bursts.

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