TITLE:   GCN CIRCULAR
NUMBER:  16134
SUBJECT: Konus-Wind observation of GRB 140419A
DATE:    14/04/20 15:07:10 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

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

The long-duration, intense GRB 140419A
(Swift-BAT trigger #596426: Marshal et al., GCN 16118;
Baumgartner et al., GCN 16127)
triggered Konus-Wind at T0=14811.110 s UT (04:06:51.110).

The burst light curve shows a broad, hard-spectrum pulse
from ~T0-10 s to ~T0+40 s and a complex of narrow,
softer pulses around ~T0+50 s.
The total duration of the burst is ~80 s.
The emission is seen up to several MeV, however
the energy channels above ~2 MeV are strongly affected
by the high and variable solar particle background.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB140419_T14811/

As observed by Konus-Wind, the burst
had a fluence of 5.8(-1.9,+2.8)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+7.744 s,
of 4.7(-1.9,+1.8)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+76.032 s)
is best fit in the 20 keV - 1.9 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.63 (-0.22,+0.36),
the high energy photon index beta = -2.3 (-2.5,+0.4),
the peak energy Ep = 293 (-84,+84) keV,
chi2 = 51.1/59 dof.

The spectrum near the maximum count rate
(measured from T0+6.144 to T0+17.408 s)
is best fit in the 20 keV - 1.9 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.52 (-0.20,+0.24),
the high energy photon index beta = -2.3 (-2.7,+0.4),
the peak energy Ep = 363 (-75,+96) keV,
chi2 = 70.7/60 dof.

Assuming the redshift z=3.956 (Tanvir et al., GCN 15645)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.27, and Omega_Lambda = 0.73,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~1.9x10^54 erg,
the peak luminosity L_iso is ~7.5x10^53 erg/s,
and the rest-frame peak energy Ep,i is ~1450 keV.
These estimates place GRB 140419A among the most
energetic GRBs.

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