Konus-Wind detection of two bright bursts from SGR 1935+2154

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.