TITLE: GCN CIRCULAR NUMBER: 37613 SUBJECT: Konus-Wind detection of GRB 240905B DATE: 24/09/26 15:50:34 GMT FROM: Dmitry Svinkin at Ioffe Institute svinkin@mail.ioffe.ru

D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, report:

The short-duration GRB 240905B (Fermi-GBM detection: The Fermi GBM team, GCN 37389; Dalessi et al., GCN 37436; AstroSat-CZTI detection: Joshi et al, GCN 37391; Fermi-LAT detection: Gupta et al., GCN 37418; IPN triangulation: Kozyrev et al., GCN 37455; VZLUSAT-2 detection: Dafcikova et al., GCN 37601) triggered Konus-Wind at T0=16038.558 s UT (04:27:18.558).

The burst light curve shows a multipeaked structure which starts at ~T0-0.1 s and has a total duration of ~1 s. The emission is seen up ~5 MeV.

The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB240905_T16038/

As observed by Konus-Wind, the burst had a fluence of 1.68(-0.28,+0.35)x10^-5 erg/cm2, and a 16-ms peak flux, measured from T0+0.432 s, of 4.13(-1.05,+1.17)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+8.448 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.54(-0.18,+0.21) and Ep = 1229(-251,+357) keV (chi2 = 92/87 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.2 (chi2 = 92/86 dof).

All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.

View this GCN Circular online at https://gcn.nasa.gov/circulars/37613. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...