TITLE:   GCN CIRCULAR
NUMBER:  21148
SUBJECT: Konus-Wind observation of GRB 170524B
DATE:    17/05/26 11:33:22 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@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 170524B (Swift/BAT detection: Barthelmy et al., GCN 21142)
triggered Konus-Wind at T0=38438.475 s UT (10:40:38.475).

The KW light curve shows a multi-peaked emission with a total duration
of ~24 s.
The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst had a fluence of
(5.7 ± 0.4)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0+1.644, of (1.44 ± 0.10)x10^-5 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+21.760 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 = -0.85(-0.06,+0.06),
and the peak energy Ep = 766(-74,+87) keV,
chi2 = 93/98 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 = 93/97 dof.

The spectrum near the peak count rate (measured from T0 to T0+5.376 s)
is best fit in the 20 keV - 15 MeV range by the CPL function
with the following model parameters:
the photon index alpha = -0.72(-0.06,+0.06),
and the peak energy Ep = 860(-73,+83) keV,
chi2 = 111/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep, and an upper limit on beta of -2.7,
chi2 = 110/97 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170524_T38438/

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