TITLE: GCN CIRCULAR NUMBER: 33544 SUBJECT: Konus-Wind detection of GRB 230328B DATE: 23/03/30 14:13:25 GMT FROM: Dmitry Svinkin at Ioffe Institute svinkin@mail.ioffe.ru
D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, report:
The long-duration GRB 230328B (Fermi-GBM detection: The Fermi GBM team, GCN Circ. 33526; Swift-BAT detection: Gropp et al., GCN Circ. 33527; Markwardt et al., GCN Circ. 33541; AstroSat-CZTI detection: Waratkar et al., GCN Circ. 33532; GRBAlpha detection: Dafcikova et al., GCN Circ. 33543;) triggered Konus-Wind at T0=53688.873 s UT (14:54:48.873).
The burst light curve shows a multi-peaked structure which starts at ~T0-3.3 s and has a total duration of ~12 s. The emission is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB230328_T53688/
As observed by Konus-Wind, the burst had a fluence of 7.12(-0.51,+0.58)x10^-6 erg/cm2, and a 64-ms peak flux, measured from T0+0.430 s, of 2.87(-0.77,+0.78)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 5 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.38(-0.13,+0.14) and Ep = 151(-21,+29) keV (chi2 = 73/75 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.2 (chi2 = 74/24 dof).
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.