[vsnet-grb-info 18788] Konus-Wind observation of GRB 161202A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20238
SUBJECT: Konus-Wind observation of GRB 161202A
DATE:    16/12/06 16:44:29 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 161202A
(Swift-BAT detection and observation: Sbarufatti et al.,
GCN Circ. 20227, Cummings et al., GCN Circ. 20233;
Fermi-LAT detection: Vianello & Longo, GCN Circ. 20229)
triggered Konus-Wind at T0=83508.822 s UT (23:11:48.822).

The burst light curve shows a multipeaked structure
started at ~T0-57.1 s with a total duration of ~181.0 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/GRB161202_T83508/

As observed by Konus-Wind, the burst
had a fluence of 2.90(-0.40,+0.73)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+3.920 s,
of 3.03(-0.80,+0.80)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+139.520 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 = -1.43(-0.25,+0.30)
and Ep = 222(-63,+201) keV (chi2 = 65/62 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high-energy photon index: beta < -1.9
(chi2 = 65/61 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 the power law with exponential cutoff model:
with  alpha = -0.67(-0.21,+0.24)
and Ep = 203(-20,+26) keV (chi2 = 76/62 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high-energy photon index: beta < -2.5
(chi2 = 76/61 dof)

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