[vsnet-grb-info 16922] Konus-Wind observation of GRB 150824A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18203
SUBJECT: Konus-Wind observation of GRB 150824A
DATE:    15/08/25 16:37:18 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, 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-duration, bright GRB 150824A
(Fermi-GBM detection: Bissaldi & Burns, GCN 18201;
IPN triangulation: Hurley et al., GCN 18202)
triggered Konus-Wind at T0=6810.119 s UT (01:53:30.119).

The light curve shows several pulses in the interval
from ~T0-0.5 s to ~T0+15 s.
The emission is seen up to ~5 MeV.

As observed by Konus-Wind, the burst had a fluence
of 1.8(-0.2,+0.2)x10^-5 erg/cm2, and a 64-ms peak flux,
measured from T0+0.896 s, of 7.6(-0.8,+0.9)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+16.384 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.96 (-0.16,+0.11),
the high energy photon index beta = -3.11 (-6.89,+0.44),
the peak energy Ep = 197 (-16,+22) keV,
chi2 = 106/97 dof.

The spectrum near the peak count rate (measured from T0 to T0+8.192 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.83 (-0.11,+0.12),
the high energy photon index beta = -2.79 (-0.56,+0.29),
the peak energy Ep = 200 (-19,+20) keV,
chi2 = 90/92 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150824_T06810/

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