| Circular_text |
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
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.
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