GCN Circular 17566

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 150309A (Swift-BAT trigger #634200:
Cummings et al., GCN 17553
Not found
 
 
; Baumgartner et al., GCN 17562
Not found
 
 
)
triggered Konus-Wind at T0=82792.708 s UT (22:59:52.708).

The KW light curve shows a broad emission pulse which
starts at ~T0-7 s and decays to ~T0+55 s.
The pulse is followed by a weak soft emission detectable
up to ~T0+250 s.
The emission is visible up to ~4 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150309_T82792/

As observed by Konus-Wind, the burst had a fluence
of 4.1(-0.4,+0.5)x10^-5 erg/cm2, and a 64-ms peak flux,
measured from T0+16.832 s, of 4.0(-0.4,+0.4)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+53.248 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 = -0.79 (-0.09,+0.11),
the high energy photon index beta = -2.79 (-0.48,+0.29),
the peak energy Ep = 182 (-17,+14) keV,
chi2 = 101/97 dof.

The spectrum near the peak count rate
(measured from T0+8.448 to T0+20.480 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 = -0.64 (-0.09,+0.11),
the high energy photon index beta = -2.73 (-0.34,+0.22),
the peak energy Ep = 197 (-17,+16) keV,
chi2 = 110/97 dof.

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