[vsnet-grb-info 17610] Konus-Wind observation of GRB 160220B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19045
SUBJECT: Konus-Wind observation of GRB 160220B
DATE:    16/02/21 21:03:08 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova at mail.ioffe.ru>

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

The long-duration GRB 160220B (Swift-BAT trigger #674734:
Cummings et al., GCN 19029; Lien et al., GCN 19043)
triggered Konus-Wind at T0=40259.435 s UT (11:10:59.435).

The burst light curve shows a single pulse
started at ~T0-12.8 s with a total duration of ~33.3 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/GRB160220_T40259/

As observed by Konus-Wind, the burst
had a fluence of 1.49(-0.11,+0.11)x10^-5 erg/cm2,
and a 16-ms peak flux, measured from T0+0.896 s,
of 4.32(-1.91,+1.92)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+16.640 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.84 (-0.22,+0.25)
and Ep = 197 (-20,+26) keV (chi2 = 47/62 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 = 47/61 dof)

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+8.448 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.65 (-0.21,+0.24)
and Ep = 208 (-19,+23) keV (chi2 = 57/61 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.5
(chi2 = 57/60 dof)

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