[vsnet-grb-info 19098] Konus-Wind observation of GRB 170208B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20643
SUBJECT: Konus-Wind observation of GRB 170208B
DATE:    17/02/09 14:39:18 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin at mail.ioffe.ru>

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

The long-duration GRB 170208B
(Swift-BAT detection: Siegel et al., GCN Circ. 20632)
triggered Konus-Wind at T0=81222.750 s UT (22:33:42.750).

The burst light curve shows a single emission episode
started at ~T0-5 s with a total duration of ~11 s.
The emission is seen up to ~1 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170208_T81222/

As observed by Konus-Wind, the burst
had a fluence of 8.17(-0.44,+0.46)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+1.072 s,
of 2.55(-0.82,+0.82)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+8.448 s)
is best fit in the 20 keV - 1 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.78(-0.23,+0.25)
and Ep = 105(-7,+8) keV (chi2 = 40/51 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.0
(chi2 = 39/50 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.