GCN Circular 18233

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, very bright GRB 150902A
(Fermi LAT detection: Arimoto et al., GCN Circ. 18228
Not found
 
 
;
Fermi GBM detection: Roberts and Younes, GCN Circ. 18229
Not found
 
 
)
triggered Konus-Wind at T0=63340.850 s UT (17:35:40.850).

The burst light curve shows a single pulse with
a total duration of ~20 s followed by a weak tail up to ~100 s.
The emission is seen up to ~18 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150902_T63340/

As observed by Konus-Wind, the burst
had a fluence of 1.21(-0.07,+0.07)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+6.384 s,
of 2.13(-0.27,+0.28)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+25.600 s)
is best fit in the 20 keV - 18 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.58(-0.06,+0.07),
the high energy photon index beta = -2.30(-0.11,+0.09),
the peak energy 322(-21,+23) keV
(chi2 = 138/96 dof)

The spectrum near the maximum count rate
(measured from T0+6.144 to T0+6.656 s)
is best fit in the 20 keV - 11 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.02(-0.18,+0.21),
the high energy photon index beta = -2.75(-0.39,+0.23),
the peak energy 288(-33,+37) keV
(chi2 = 77/47 dof)

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