TITLE: GCN CIRCULAR NUMBER: 40512 SUBJECT: Konus-Wind detection of GRB 250520A (short/hard) DATE: 25/05/21 14:42:50 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 short GRB 250520A (Swift detection: Eyles-Ferris et al., GCN 40491; SVOM/GRM observation: Wang et al., GCN 40495) triggered Konus-Wind (KW) at T0=9741.866 s UT (02:42:21.866). The burst light curve shows a single pulse, which starts at ~T0-0.07 s and has a duration of ~0.26 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/GRB250520_T09741/ As observed by Konus-Wind, the burst had the total fluence of (3.38 ± 0.75)x10^-6 erg/cm^2 and a 16-ms peak energy flux, measured from T0-0.032, of (3.49 ± 0.81)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+0.192 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 = -0.48 (-0.27,+0.41), the high energy photon index beta = -2.51 (-1.99,+0.47), the peak energy Ep = 671 (-211,+247) keV, chi2 = 37/27 dof. The spectrum near the peak count rate (measured from T0 to T0+0.064 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 (-0.27,+0.46), the high energy photon index beta = -2.39 (-7.61,+0.53), the peak energy Ep = 1099 (-505,+876) keV, chi2 = 11/17 dof. 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/40512. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...