TITLE: GCN CIRCULAR NUMBER: 33579 SUBJECT: GRB 230307A: further analysis of the Konus-Wind detection and rest-frame energetics DATE: 23/04/06 16:11:37 GMT FROM: Dmitry Svinkin at Ioffe Institute D. Svinkin, D. Frederiks, A. Ridnaia, A. Tsvetkova, and A. Lysenko on behalf of the Konus-Wind team, report: Following the probable host galaxy identification (Gillanders et al. GCN Circ. 33485; Levan at al., GCN Circ. 33569), we present a further analysis of the KW detection (Svinkin et al., GCN Circ. 33427) of the extremely bright, long-duration GRB 230307A (GCNs 33405, 33406, 33407, 33410, 33411, 33412, 33413, 33414, 33415, 33416, 33418, 33424, 33425, 33461). As measured by KW the burst durations are T50=9.17+/-0.04 s and T90 = 31.2 +/-0.4 s, both in the 100-1700 keV energy band. The refined burst fluence is 4.05(-0.03,+0.03)x10^-3 erg/cm2, and a 64-ms peak flux, measured from T0+6.224 s, is 6.85(-0.27,+0.27)x10^-4 erg/cm2/s (both in the 20 keV - 10 MeV energy range). Assuming the redshift of the host galaxy z=0.065 (GCN 33485) and a standard cosmology model with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the following rest-frame parameters: the isotropic energy release E_iso is (4.21+/-0.03)x10^52 erg, the peak luminosity L_iso is (7.58 +/-0.33)x10^51 erg/s, the rest-frame peak energy of the time-integrated spectrum, Ep,i,z is (933+/-12) keV, and the rest-frame peak energy at the peak luminosity Ep,p,z is (1388+/-52) keV. With these values, GRB 230307A is outside the 90% prediction band of both 'Amati' and 'Yonetoku' relations built for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021). In both Eiso-Ep,i,z and Liso-Ep,p,z planes, GRB 230307A is shifted towards the short-hard (Type I, merger-origin) GRB population, see http://www.ioffe.ru/LEA/GRBs/GRB230307_T56645/GRB230307A_rest_frame.pdf The analysis of KW data is ongoing and its results will be reported elsewhere.