[vsnet-grb-info 24935] Konus-Wind observation of GRB 200205B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27034
SUBJECT: Konus-Wind observation of GRB 200205B
DATE:    20/02/11 13:05:44 GMT
FROM:    Anastasia Tsvetkova at Ioffe Institute  <tsvetkova at mail.ioffe.ru>

A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Lysenko, A. Ridnaia and T. Cline
on behalf of the Konus-Wind team, report:

The long GRB 200205B which triggered Swift/BAT
at T0=T0(BAT)=19:21:43 UT
(Swift/BAT detection: Evans et al., GCN 26993;
Ukwatta et al., GCN 27012;)
was detected by Konus-Wind in the waiting mode.

The burst light curve shows two emission episodes:
the first pulse lasts from ~T0+48.6 s to ~T0+89.8 s,
and the second pulse lasts from ~T0+390.1 s to ~T0+525.5 s.
The total duration of the burst is ~477 s.

As observed by Konus-Wind, the burst had a fluence of
1.12(-0.05,0.26)x10^-5 erg/cm2 and a 2.944-s peak flux,
measured from ~T0(BAT)+437.202 s, of 1.55(-0.09,+0.44)x10^-7 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

Fitting the K-W 3-channel spectrum o the initial pulse
(from ~T0(BAT)+48.594 s to ~T0(BAT)+89.810 s)
in the 20 keV - 1.5 MeV range
by a simple power law model yields
the PL index = 2.34(-0.06,+0.17),
chi2 = 2.95 / 1 dof.

Modelling the K-W 3-channel spectrum of the second pulse
(from ~T0(BAT)+390.098 s to ~T0(BAT)+446.034 s)
in the 20 keV - 1.5 MeV range
by a power law with exponential cutoff model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields
alpha = -1.32(-0.59,+2.70),
and Ep =87(-17,+13) keV.

Assuming the redshift z=1.465 (Vielfaure et al., GCN 26998)
and a standard cosmology model with H_0 = 67.3 km/s/Mpc,
Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~6.5x10^52 erg,
the peak luminosity L_iso is ~2.2x10^51 erg/s,
and the rest-frame peak energy of the initial pulse spectrum,
Ep,z, is ~ 214 keV.

All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.

The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB200205B/