GCN Circular 29373
Subject
Konus-Wind detection of two bright bursts from SGR 1935+2154
Date
2021-01-29T16:39:15Z (3 years ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@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:
Two bright, short bursts from SGR 1935+2154
(GECAM detection: Huang et al., GCN Circ. 29363
IPN triangulation: Ridnaia et al., GCN Circ. 29365)
triggered Konus-Wind on 2021 January 27 at
24616.685 s UT (06:50:16.685), hereafter burst #1; and
on 2021 January 29 at 25196.932 s UT (06:59:56.932), burst #2.
The burst light curves feature a sharp rise,
followed by a gradual decay, and, finally,
a quick return of a count rate to the background level.
Additionally, the main pulse of burst #1 is preceded by
a weaker, partially overlapped sub-pulse.
The burst total durations are ~100 ms (#1) and ~200 ms (#2).
The emission in both bursts is seen up to ~200 keV.
As measured by KW, the burst fluences and peak fluxes are as follows:
------------------------------------------------------------------
# Date T0(KW) s UT Fl* PF**
------------------------------------------------------------------
1 20210127 24616.685 s UT(06:50:16.685) 0.91 +/-0.07 16.0 +/-3.2
2 20210129 25196.932 s UT(06:59:56.932) 3.14 +/-0.11 27.5 +/-4.4
------------------------------------------------------------------
* - Fluence (20-500 keV) in units of 1e-6 erg/cm2
** - Peak Flux (20-500 keV) on 2-ms time scale
in units of 1e-6 erg/cm2/s
Time-averaged spectra of the bursts are well fit
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with the following parameters:
-------------------------------------------------------------
# Tbeg-Tend alpha Ep(keV) chi2/dof
-------------------------------------------------------------
1 0 - 0.064 -0.21(-1.00,+1.20) 31(-10,+5) 13/11
2 0 - 0.192 -0.33(-0.37,+0.40) 34(-3,+3) 14/20
-------------------------------------------------------------
These spectral parameters are typical of a few dosen SGR 1935+2154
short bursts detected by KW previously (with the notable exception
of the April 28 SGR/FRB event).
The Konus-Wind light curves of the bursts are available at
http://www.ioffe.ru/LEA/SGRs/210127_T24616/
http://www.ioffe.ru/LEA/SGRs/210129_T25196/
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.