TITLE:   GCN CIRCULAR
NUMBER:  14262
SUBJECT: Konus-Wind observation of GRB 130305A
DATE:    13/03/06 12:14:28 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:

The long-duration intense GRB 130305A
(Swift-BAT trigger #550329: Cumings & Palmer, GCN 14257;
Fermi-LAT detection: Guiriec et al., GCN 14260;
Fermi-GBM observation: Yu and Xiong, GCN 14261)
triggered Konus-Wind at T0=41953.135s UT (11:39:13.135)

The light curve shows a bright hard pulse with
a total duration of ~30 s followed by a weaker
hard emission tail out to ~T0+250 s.
The emission in the main bursting episode is seen up to 12 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB130305_T41953/

As observed by Konus-Wind, the main pulse
had a fluence of (8.5 ± 0.6)x10-5 erg/cm2,
and a 64-ms peak flux, measured from T0+4.480 s,
of (1.6 ± 0.1)x10-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+36.096 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 = -0.81 ± 0.04,
the high energy photon index beta = -2.5 ± 0.2,
the peak energy Ep = 640 ± 45 keV,
chi2 = 83.7/95 dof.

The spectrum at the maximum count rate (measured from T0 to T0+11.520 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 = -0.72 ± 0.04,
the high energy photon index beta = -2.8 ± 0.2,
the peak energy Ep = 655 ± 30 keV,
chi2 = 89.5/96 dof.

The spectrum of the emission tail (measured from T0+36.096 to T0+224.512 s)
is best fit in the 20 keV - 10 MeV range by the simple power-law model
with a rather hard photon index of (-1.4 ± 0.1), chi2 = 71.7/89 dof.
The emission in this time interval is seen up to 9 MeV
and the 20 keV - 10 MeV energy fluence is (3.3 ± 1.1)x10-5 erg/cm2.

All the quoted results are preliminary.