TITLE: GCN CIRCULAR NUMBER: 44474 SUBJECT: Konus-Wind detection of GRB 260504B (short/hard) DATE: 26/05/05 14:25:39 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 260504B (SVOM/ECLAIRs detection: Saccardi et al., GCN 44454; SVOM/GRM detection: Wang et al., GCN 44470; GECAM-B detection: Wang et al., GCN 44473) triggered Konus-Wind (KW) at T0=34281.198 s UT (09:31:21.198). The burst light curve shows a single pulse, which starts at ~T0-0.05 s and has a duration of ~0.21 s. The emission is seen up to ~6 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260504_T34281/ As observed by Konus-Wind, the burst had the total fluence of (2.39 ± 0.52)x10^-6 erg/cm^2 and a 16-ms peak energy flux, measured from T0-0.032, of (2.06 ± 0.45)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 fitted in the 20 keV - 15 MeV range by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.00 (-0.12, + 0.14) and Ep = 1461(-398,+584) keV, chi^2 = 34/32 dof. Fitting this spectrum by a Band GRB function yields the same values of alpha and Ep, and only an upper limit on the high energy photon index beta of -2.1 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/44474. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...