[vsnet-grb-info 18029] Konus-Wind observation of GRB 160530A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19477
SUBJECT: Konus-Wind observation of GRB 160530A
DATE:    16/05/31 16:16:26 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, very intense GRB 160530A
(COSI detection: Tomsick, GCN Circ. 19473;
IPN triangulation: Svinkin et al., GCN circ. 19476)
triggered Konus-Wind at T0=25426.549 s UT (07:03:46.549).

The burst light curve shows a multipeaked structure
started at ~T0-0.1 s with a total duration of ~37 s.
The emission is seen up to ~5 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160530_T25426/

As observed by Konus-Wind, the burst
had a fluence of 1.30(-0.04,+0.04)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+2.416 s,
of 3.70(-0.38,+0.38)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+38.912 s)
is best fit in the 20 keV - 5 MeV range
by a power law with exponential cutoff (CPL) model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.93(-0.03,+0.03)
and Ep = 638(-33,+36) 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 < -3.5
(chi2 = 73/72 dof)

The spectrum near the maximum count rate
(measured from T0+1.792 to T0+2.560 s)
is best fit in the 20 keV - 7 MeV range
by the CPL model
with alpha = -0.23(-0.09,+0.10)
and Ep = 714(-50,+55) keV (chi2 = 53/62 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.9
(chi2 = 50/61 dof)

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