TITLE: GCN CIRCULAR NUMBER: 39283 SUBJECT: Konus-Wind detection of GRB 250206A DATE: 25/02/11 13:48:06 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 long-duration GRB GRB 250206A (Fermi-GBM detection: Fermi GBM team, GCN 39172; BALROG localization: Preis & Greiner, GCN 39173; Fermi-LAT detection: Gupta et al., GCN 39233; EIRSAT-1 GMOD detection: Murphy et al., GCN 39236) triggered Konus-Wind at T0=71491.594 s UT (19:51:31.594).
The burst light curve shows two multipeaked episodes started at ~T0-3.6 s with a total duration of ~75.6 s. The emission is seen up to ~4 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250206_T71491/
As observed by Konus-Wind, the burst had a fluence of 2.44(-0.09,+0.10)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+9.072 s, of 2.91(-0.44,+0.44)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+73.984 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 = -0.76(-0.10,+0.11) and Ep = 205(-11,+13) keV (chi2 = 87/98 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.4 (chi2 = 85/97 dof).
The spectrum near the maximum count rate (measured from T0+8.448 to T0+16.640 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 = -0.06(-0.13,+0.13) and Ep = 223(-9,+10) keV (chi2 = 85/82 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -3.4 (chi2 = 85/81 dof).
All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.
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