[vsnet-grb-info 18614] Konus-Wind observation of GRB 161015A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20062
SUBJECT: Konus-Wind observation of GRB 161015A
DATE:    16/10/17 13:30:12 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 161015A
(Fermi-LAT detection: Masanori Ohno et al., GCN Circ. 20054;
Fermi-GBM detection: Stanbro and Meegan, GCN Circ. 20056;
AstroSat-CZTI detection: Kumar et al., GCN Circ. 20060)
triggered Konus-Wind at T0=61386.899 s UT (17:03:06.899).

The burst light curve shows multipeaked structure
starting at ~T0-0.5 s and having a total duration of ~16 s.
The emission is seen up to 3 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB161015_T61386/

As observed by Konus-Wind, the burst
had a fluence of 1.11(-0.08,+0.09)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+1.888 s,
of 4.01(-0.84,+0.85)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 - 4 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.12(-0.12,+0.13)
and Ep = 215(-26,+34) keV (chi2 = 60/73 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.6
(chi2 = 60/72 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 - 4 MeV range
by a power law with exponential cutoff model:
with  alpha = -0.68(-0.14,+0.16)
and Ep = 256(-26,+32) keV (chi2 = 73/73 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.2
(chi2 = 73/72 dof)

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