[vsnet-grb-info 19983] Konus-Wind observation of GRB 171027A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22070
SUBJECT: Konus-Wind observation of GRB 171027A
DATE:    17/10/29 17:43:50 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

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

The long GRB 171027A (Swift-BAT trigger #783479: (D'Avanzo et al.,
GCN  22053; Lien et al., GCN 22066; T0(BAT)=08:23:06.623 UT)
was detected by Konus-Wind (KW) in the waiting mode.

The light curve shows a muli-peaked structure with a duration of ~103 s.
Modeling the KW 3-channel time-integrated spectrum
(from T0(BAT)-1.661 s to T0(BAT)+101.379 s) by
a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.21(-0.35,+0.20) and Ep = 176(-35,+47) keV.
The energy fluence for this time interval is (1.78 ± 0.21)x10^-5
erg/cm2, and the peak energy flux, measured on a 2.944 s scale from
T0(BAT)+63.107 s is (6.6 ± 0.12)x10^-7 erg/cm2/s, both in the
20 keV-10 MeV range.

Assuming the GRB photo-z < 3.85 (90%, Butler et al., GCN 22061)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.30, and Omega_Lambda = 0.70, our analysis sets
the following upper limits on the burst isotropic energy release
and rest-frame peak energy: E_iso < 5.2x10^53 erg and
Ep,z < 854 keV.

The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB171027A/

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