GCN Circular 33511

A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long-duration GRB 230309A
(AstroSat CZTI detection: Waratkar et al., GCN Circ. 33464
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 ;
IPN triangulation: Kozyrev et al., GCN Circ. 33484
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 )
triggered Konus-Wind at T0=45138.667 s UT (12:32:18.667).

The burst light curve shows a multipeaked structure
which starts at ~T0-6.1 s and has a total duration of ~68.9 s.
The emission is seen up to ~4 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB230309_T45138/

As observed by Konus-Wind, the burst
had a fluence of 1.69(-0.11,+0.12)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+3.232 s,
of 3.12(-0.39,+0.40)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+62.976 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.80(-0.07,+0.08),
the high energy photon index beta = -2.27(-0.15,+0.11),
the peak energy Ep = 305(-25,+29) keV
(chi2 = 96/97 dof).

The spectrum near the maximum count rate
(measured from T0+2.816 to T0+3.584 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.55(-0.10,+0.12),
the high energy photon index beta = -2.80(-0.63,+0.31),
the peak energy Ep = 483(-64,+66) keV
(chi2 = 57/55 dof).

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