[vsnet-grb-info 19446] Konus-Wind observation of GRB 170527A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21166
SUBJECT: Konus-Wind observation of GRB 170527A
DATE:    17/05/30 16:11:27 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

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

The long GRB 170527A (IPN localization: Hurley et al., GCN 21164)
triggered Konus-Wind at T0=41466.714 s UT (11:31:06.714).

The KW light curve shows a multi-peaked emission with a total duration
of ~57 s. The emission is seen up to ~5 MeV.

As observed by Konus-Wind, the burst had a fluence of
(8.9 ± 0.6)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0+0.640, of (1.79 ± 0.13)x10^-5 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+48.128 s)
is best fit in the 20 keV - 15 MeV range by a cutoff power-law
(CPL) function with the following model parameters:
the photon index alpha = -0.71(-0.09,+0.09),
and the peak energy Ep = 571(-47,+55) keV,
chi2 = 103/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep and an upper limit on beta of -2.5,
chi2 = 102/97 dof.

The spectrum near the peak count rate (measured from T0 to T0+7.168 s)
is best fit in the 20 keV - 15 MeV range by the CPL function
with the following model parameters:
the photon index alpha = -0.23(-0.10,+0.10),
and the peak energy Ep = 714(-44,+48) keV,
chi2 = 113/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep, and an upper limit on beta of -3.9,
chi2 = 113/97 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170527_T41466/

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.