TITLE: GCN CIRCULAR NUMBER: 43712 SUBJECT: Konus-Wind detection of GRB 260207B DATE: 26/02/12 14:06:38 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 short-duration GRB with extended emission (EE) GRB 260207B (Fermi-GBM detection: Fermi GBM team, GCN 43629; Sonawane & Bala, GCN 43634; GECAM-B detection: Zao et al., GCN 43644; AstroSat-CZTI detection: Goyal et al., GCN 43680; IPN triangulation: Kozyrev et al., GCN 43691; GRID detection: Zeng et al., GCN 43710) triggered Konus-Wind at T0=47529.467 s UT (13:12:09.467). The burst light curve shows a short initial pulse, which starts at ~T0-40 ms and has a duration of ~220 ms. The initial pulse is followed by a weaker extended emission (EE), starting at ~T0+9 s, peaking at ~T0+43 s, and lasting up to ~T0+95 s. The emission in the initial pulse is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260207_T47529/ As observed by Konus-Wind, the initial pulse had the fluence of 2.66(-0.19,+0.20)x10^-6 erg/cm2, and the 16-ms peak flux, measured from T0+0.104 s, of 4.41(-0.54,+0.58)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the initial pulse (measured from T0 to T0+0.192 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 = -0.99(-0.08,+0.08) and Ep = 495(-60,+72) keV (chi2 = 44/43 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -3.1 (chi2 = 44/42 dof). The time-averaged spectrum of the EE (measured from T0+8.448 s to T0+73.984 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: with alpha = -1.67(-0.21,+0.24) and Ep = 44 (-19,+11) keV (chi2 = 93/98 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -3.0 (chi2 = 93/97 dof). From this spectrum, the total EE fluence is 5.02(-0.4,+0.4)x10^-6 erg/cm2, a factor of ~2 higher than that of the initial pulse. 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/43712. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...