TITLE: GCN CIRCULAR NUMBER: 39720 SUBJECT: Konus-Wind detection of GRB 250308A DATE: 25/03/14 15:54:17 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 250308A (SVOM-GRM detection: Wang et al., GCNs 39632, 39636; IPN triangulation: Kozyrev et al., GCN 39653; CALET-GBM detection: Kawakubo et al., GCN 39663; Swift-BAT/GUANO detection: DeLaunay et al., GCN 39676) triggered Konus-Wind at T0=65194.997 s UT (18:06:34.997).
The burst light curve shows a multipeaked structure which starts at ~T0-40 ms and has a total duration of ~0.4 s. The emission is seen up to ~5 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250308_T65194/
As observed by Konus-Wind, the burst had a fluence of 8.23(-0.52,+0.54)x10^-6 erg/cm2, and a 16-ms peak flux, measured from T0-6 ms, of 5.24(-0.69,+0.70)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 - 5 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.41(-0.12,+0.13) and Ep = 1176(-109,+125) keV (chi2 = 60/52 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.9 (chi2 = 60/51 dof).
All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.
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