TITLE: GCN CIRCULAR NUMBER: 42473 SUBJECT: Konus-Wind detection of GRB 251016A (short/hard) DATE: 25/10/27 12:47:24 GMT FROM: Valentina Panteleeva at Ioffe Institute panteleevav228@gmail.com

V. Panteleeva, 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-duration GRB 251016A (SVOM/ECLAIRs detection: Basa et al., GCN 42308; Brunet et al., GCN 42374; Fermi-GBM detection: The Fermi GBM team, GCN 42309; Smith and Meegan, GCN 42365; Glowbug detection: Woolf et al., GCN 42313; CALET-GBM detection: Kawakubo et al., GCN 42321; AstroSat-CZTI detection: Arya et al., GCN 42327; Insight-HXMT/HE detection: Zao et al., GCN 42359) triggered Konus-Wind at T0=53956.564 s UT (14:59:16.564).

The burst light curve shows a single pulse which starts at ~T0-0.2 s and has a total duration of ~0.5 s. The emission is seen up to ~3 MeV.

The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB251016_T53956/

As observed by Konus-Wind, the burst had the total fluence of 6.32(-0.91,+1.04)x10^-6 erg/cm2, and the 16-ms peak flux, measured from T0+0.018 s, of 2.46(-0.52,+0.58)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+0.256 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 = -0.44(-0.20,+0.35), the high energy photon index beta = -2.14(-0.72,+0.34), the peak energy Ep = 825(-282,+293) keV (chi2 = 30/25 dof).

All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.

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