TITLE: GCN CIRCULAR NUMBER: 33511 SUBJECT: Konus-Wind detection of GRB 230309A DATE: 23/03/23 13:14:16 GMT FROM: Anna Ridnaia at Ioffe Institute A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 230309A (AstroSat CZTI detection: Waratkar et al., GCN Circ. 33464; IPN triangulation: Kozyrev et al., GCN Circ. 33484) triggered Konus-Wind at T0=45138.667 s UT (12:32:18.667). The burst light curve shows a multipeaked structure which starts at ~T0-6.1 s and has a total duration of ~68.9 s. The emission is seen up to ~4 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB230309_T45138/ As observed by Konus-Wind, the burst had a fluence of 1.69(-0.11,+0.12)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+3.232 s, of 3.12(-0.39,+0.40)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+62.976 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.80(-0.07,+0.08), the high energy photon index beta = -2.27(-0.15,+0.11), the peak energy Ep = 305(-25,+29) keV (chi2 = 96/97 dof). The spectrum near the maximum count rate (measured from T0+2.816 to T0+3.584 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.55(-0.10,+0.12), the high energy photon index beta = -2.80(-0.63,+0.31), the peak energy Ep = 483(-64,+66) keV (chi2 = 57/55 dof). All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.