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GCN Circular 18073

Subject
Konus-Wind observation of GRB 150725A
Date
2015-07-27T09:11:27Z (9 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, 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 150725A (Masumitsu et al., GCN Circ. 18062) 
triggered Konus-Wind at T0=31454.410 s UT (08:44:14.410),
~15 s before the MAXI trigger.

The KW light curve measured in the triggered mode shows multiple
bright pulses in the interval from ~T0-0.5 s to ~T0+60 s.
The emission is visible up to ~10 MeV.

As observed by Konus-Wind, the burst had a fluence
of 1.55(-0.10,+0.09)x10^-4 erg/cm2, and a 64-ms peak flux,
measured from T0+51.456 s, of 1.35(-0.23,+0.17)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+58.112 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 = -0.84 (-0.07,+0.08),
the high energy photon index beta = -2.32 (-0.13,+0.10),
the peak energy Ep = 326 (-24,+28) keV,
chi2 = 125/97 dof.

The spectrum near the peak count rate
(measured from T0+51.200 to T0+58.112 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 = -0.77 (-0.23,+0.26),
the high energy photon index beta = -2.29 (-0.52,+0.18),
the peak energy Ep = 270 (-53,+86) keV,
chi2 = 92/97 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150725_T31454/

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