TITLE: GCN CIRCULAR NUMBER: 32152 SUBJECT: Konus-Wind observation of GRB 220527A DATE: 22/05/30 16:59:09 GMT FROM: Alexandra Lysenko at Ioffe Institute A. Lysenko, D. Frederiks, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 220527A (AGILE detection: Ursi et al., GCN Circ. 32129; Fermi-LAT detection: Bissaldi et al., GCN Circ. 32131; Fermi-GBM detection: The Fermi GBM team, GCN Circ. 32130; Mangan et al., GCN Circ. 32133; CALET detection: Yamaoka et al., GCN Circ. 32139; AstroSat CZTI detection: Gopalakrishnan et al., GCN Circ. 32140) triggered Konus-Wind at T0=33441.517 s UT (09:17:21.517). The burst light curve shows a multipeaked structure which starts at ~T0-4.1 s and has a total duration of ~21.3 s. The emission is seen up to ~16 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB220527_T33441/ As observed by Konus-Wind, the burst had a fluence of 5.98(-0.31,+0.32)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+5.152s, of 1.73(-0.21,+0.22)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+13.568 s) is best fit in the 20 keV - 16 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.80(-0.12,+0.13), the high energy photon index beta = -2.55(-0.13,+0.10), the peak energy Ep = 154(-10,+10) keV (chi2 = 115/98 dof). The spectrum near the maximum count rate (measured from T0+3.584 to T0+5.376 s) is best fit in the 20 keV - 16 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.49(-0.18,+0.21), the high energy photon index beta = -3.24(-0.53,+0.31), the peak energy Ep = 146(-9,+9) keV (chi2 = 72/64 dof). For both spectra, we note a prominent count excess over the model at energies above ~5 MeV. The excess can be modeled by an additional power-law component with a photon index of <~2. Assuming the redshift z=0.857 (Xu et al., GCN Circ. 32141) and a standard cosmology model with H_0 = 67.7 km/s/Mpc, Omega_M = 0.310, and Omega_Lambda = 0.689 (Planck Collab 2018, Paper VI), we estimate the following rest-frame parameters: the isotropic energy release E_iso is 1.22(-0.06,+0.07)x10^53 erg, the peak luminosity L_iso is 6.53(-0.81,+0.84)x10^52 erg/s, and the rest-frame peak energy of the time-integrated spectrum, Ep,i,z is 286(-18,+19) keV With the obtained estimates, GRB 220527A lies inside 68% prediction bands for both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB220527_T33441/GRB220527A_rest_frame.pdf All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.