TITLE: GCN CIRCULAR NUMBER: 35377 SUBJECT: Konus-Wind detection of GRB 231215A DATE: 23/12/16 18:27:11 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long, bright GRB 231215A (Swift detection: D'Avanzo et al., GCN 35343; AstroSat CZTI detection: Navaneeth et al., GCN 35352; CALET Gamma-Ray Burst Monitor detection: Cannady et al., GCN 35368; AGILE detection: Verrecchia et al., GCN 35361; Fermi GBM detection: Lesage et al., GCN 35369) triggered Konus-Wind (KW) at T0=35239.795 s UT (09:47:19.795). The burst light curve shows a single multi-peaked pulse, which starts at ~T0-1 s, peaks at ~T0+9.5 s, and has a total duration of ~25 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB231215_T35239/ As observed by Konus-Wind, the burst had a fluence of (1.02 ± 0.09)x10^-4 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 28.352 s, of (1.14 ± 0.12)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+24.320 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.67 (-0.07,+0.08), the high energy photon index beta = -2.49 (-0.43,+0.22), the peak energy Ep = 612 (-63,+74) keV, chi2 = 80/97 dof. The spectrum near the peak count rate (measured from T0+6.400s to T0+9.984s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.49 (-0.09,+0.09), the high energy photon index beta = -3.07 (-2.04,+0.44), the peak energy Ep = 582 (-54,+58) keV, chi2 = 69/80 dof. Assuming the redshift z=2.305 (Thoene et al., GCN 35373) 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 burst isotropic energy release E_iso to (1.35 ± 0.12)x10^54 erg, the isotropic peak luminosity L_iso to (4.93 ± 0.49)x10^53 erg/s, the rest-frame peak energy of the time-integrated spectrum Ep,i,z to ~2023 keV, and the rest-frame peak energy at the peak of the emission Ep,p,z to ~1924 keV. With the obtained estimates, GRB 230818A is inside 68% prediction band for both 'Amati' and 'Yonetoku' relations derived 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/GRB231215_T35239/GRB231215A_rest_frame.pdf All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/35377. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...