[vsnet-grb-info 25454] Konus-Wind observation of a bright burst from SGR 1935+2154

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27554
SUBJECT: Konus-Wind observation of a bright burst from SGR 1935+2154
DATE:    20/04/12 15:26:22 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia at mail.ioffe.ru>

A. Ridnaia, S. Golenetskii, R. Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:

The bright burst from SGR 1935+2154
(IPN triangulation: Svinkin et al., GCN Circ. 27527,
Fermi GBM observation: Veres et al., GCN Circ. 27531)
triggered Konus-Wind at T0=35032.256 s UT (09:43:52.256)
on 2020 April 10.

The light curve shows a single pulse with a sharp rise
and a total duration of ~0.2 s.
The emission is seen up to ~200 keV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/SGRs/200410_T35032/

As observed by Konus-Wind, the burst
had a fluence of 1.55(-0.08,+0.08)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0-0.054 s,
of 1.54(-0.15,+0.15)x10^-5 erg/cm2/s
(both in the 20 - 200 keV energy range).

The burst spectrum (measured from T0 to T0+0.128 s)
is well fit by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.15(-0.85,+0.99)
and Ep = 28(-7,+4) keV (chi2 = 15/14 dof).
A double blackbody function fits this spectrum equally well
(chi2 = 15/13 dof), with
the cold BB temperature of 6.9 (-4.6,+1.4) keV and
the hot BB temperature of 13.0 (-3.6,+7.8) keV.

Although this burst is more than order of magnitude less
energetic than the 1.7s-long "intermediate" flare (IF) from
this source on 2015 April 12 (Kozlova et al. 2016, MNRAS 460,
2008), its peak luminosity is almost comparable to that of the IF.

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