TITLE: GCN CIRCULAR NUMBER: 41941 SUBJECT: Konus-Wind detection of GRB 250920A DATE: 25/09/22 18:33:59 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report: The bright, long-duration GRB 250920A (Ferm-GBM detection: The Fermi GBM team, GCN 41895; Sonawane and Smith, GCN 41918; BALROG localization: Preis and Greiner, GCN 41896 AstroSat-CZTI detection: Harsha et al., GCN 41899; SVOM-GRM detection: Wang et al., GCN 41912; NuSTAR-detection: Waratkar et al., GCN 41926; IPN triangulation: Kozyrev et al., GCN 41940) triggered Konus-Wind at T0=10444.538 s UT (02:54:04.538). The burst light curve shows a multipeaked structure which starts at ~T0-1.1 s and has a total duration of ~12.5 s. The emission is seen up to ~15 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250920_T10444/ There are no data for the ~18-70 keV band in the triggered mode. As observed by Konus-Wind, the burst had the total fluence of 4.52(-0.15,+0.15)x10^-5 erg/cm2, and the 64-ms peak flux, measured from T0+1.984 s, of 4.06(-0.28,+0.28)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+18.432 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 = -0.84(-0.05,+0.05), the high energy photon index beta = -2.61(-0.09,+0.08), the peak energy Ep = 162(-6,+6) keV (chi2 = 106/97 dof). The spectrum near the maximum count rate (measured from T0+1.792 to T0+2.048 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 = -0.58(-0.09,+0.09), the high energy photon index beta = -2.46(-0.14,+0.11), the peak energy Ep = 332(-27,+31) keV (chi2 = 44/46 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/41941. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...