TITLE: GCN CIRCULAR NUMBER: 30197 SUBJECT: Konus-Wind detection of GRB 210610A DATE: 21/06/11 11:56:36 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, S. Golenetskii, A.Lysenko, D. Svinkin, A. Ridnaya, A. Tsvetkova, M. Ulanov, and T. Cline, report: The long GRB 210610A (Swift-BAT detection: Page et al., GCN 30160; Barthelmy et al., GCN 30186), T0 (BAT) = 15:03:43/387, was detected by Konus-Wind (KW) in the waiting mode. A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band reveals a ~8 sigma count rate increase over background in the interval from ~T0(BAT)-2 s to ~T0(BAT)+4 s. The KW light curve of this burst is available at http://www.ioffe.ru/LEA/GRBs/GRB210610A/ Modeling the KW 3-channel spectrum by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -0.17(-0.83,+1.15) and Ep = 148(-63,+87) keV. In the 10 keV -10 MeV band, the total burst fluence is (1.3 ± 0.5)x10^-6 erg/cm^2, and the 2.944 s peak energy flux is (2.7 ± 0.8)x10^-7 erg/cm^2. Assuming the redshift z=3.54 (Zhu et al., GCN 30164) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the isotropic energy release E_iso to ~3.5x10^52 erg, the isotropic luminosity L_iso to ~3.3x10^52 erg/s, and the rest-frame peak energy of the time-integrated spectrum Ep,z to ~670 keV. With these values, GRB 210610A is within 90% prediction bands for for the 'Amati' relation for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2021, ApJ, 908, 83), see http://www.ioffe.ru/LEA/GRBs/GRB210610A/GRB210610A_rest_frame.pdf All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary.