GCN Circular 19462

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

The long-duration GRB 160521B
(Fermi-GBM detection: Yu and Veres, GCN 19443
Not found
 
 
;
Fermi-LAT detection: Axelsson et al., GCN 19444
Not found
 
 
)
triggered Konus-Wind at T0=33237.337 s UT (09:13:57.337).

The burst light curve shows a broad, multi-peaked pulse
started at ~T0-0.3 s with a total duration of ~6.4 s.
The emission is seen up to ~2 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160521_T33237/

As observed by Konus-Wind, the burst
had a fluence of 1.32(-0.15,+0.17)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+1.504 s,
of 1.01(-0.14,+0.14)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+9.984 s)
is best fit in the 20 keV - 2 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.65(-0.14,+0.16),
the high energy photon index beta = -2.72(-0.49,+0.26),
the peak energy Ep = 165(-16,+17) keV
(chi2 = 49/61 dof)

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+1.792 s)
is best fit in the 20 keV - 2 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.43(-0.12,+0.14),
the high energy photon index beta = -3.62(-6.38,+0.62),
the peak energy Ep = 190(-15,+15) keV
(chi2 = 56/50 dof)

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