TITLE: GCN CIRCULAR NUMBER: 39205 SUBJECT: Konus-Wind detection of GRB 250204B DATE: 25/02/07 15:46:33 GMT FROM: Anna Ridnaia at Ioffe Institute ridnaia@mail.ioffe.ru
A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
The short-duration GRB 250204B (Fermi-GBM detection: Fermi GBM team, GCN 39141; AstroSat CZTI detection: Dasgupta et al., GCN 39142; IPN triangulation: Svinkin et al., GCN 39145; SVOM/GRM observation: Zhang et al., GCN 39163) triggered Konus-Wind at T0=24073.659 s UT (06:41:13.659).
The burst light curve shows a single pulse which starts at ~T0-0.1 s and has a total duration of ~1.5 s. The emission is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250204_T24073/
As observed by Konus-Wind, the burst had a fluence of 2.99(-0.29,+0.37)x10^-6 erg/cm2, and a 16-ms peak flux, measured from T0+0.008 s, of 7.51(-1.64,+1.74)x10^-6 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 a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.85(-0.17,+0.19) and Ep = 383(-66,+92) keV (chi2 = 16/22 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.1 (chi2 = 16/21 dof).
All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.
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