GCN Circular 23943

A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 190304A
(IPN Triangulation: Hurley et al., GCN Circ. 23942
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triggered Konus-Wind at T0=70641.622 s UT (19:37:21.622).

The burst light curve shows a double-peaked structure
started at ~T0-1.6 s with a total duration of ~3.3 s.
The emission is seen up to ~1 MeV.

As observed by Konus-Wind, the burst
had a fluence of 2.48(-0.35,+0.38)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0-0.028 s,
of 4.70(-1.01,+1.03)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 1 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.61(-0.56,+0.69)
and Ep = 97(-15,+22) keV (chi2 = 84/60 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.4
(chi2 = 84/59 dof).

The spectrum near the maximum count rate
(measured from T0 to T0+0.256 s)
is best fit in the 20 keV - 1 MeV range
by a power law with exponential cutoff model
with  alpha = -0.15(-0.43,+0.49)
and Ep = 153(-19,+25) keV (chi2 = 22/22 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.6
(chi2 = 21/21 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB190304_T70641/

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