TITLE:   GCN CIRCULAR
NUMBER:  24652
SUBJECT: Konus-Wind observation of GRB 190519A
DATE:    19/05/22 12:54:15 GMT
FROM:    Anastasia Tsvetkova at Ioffe Institute  <tsvetkova@mail.ioffe.ru>

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

The long-duration GRB 190519A
(Fermi GBM observation: Fermi GBM team, GCN 24594; von Kienlin, GCN 24596;
Swift detection: Ukwatta et al., GCN 24595; Lien et al., GCN 24606;
CALET Gamma-Ray Burst Monitor detection: Yamaoka et al., GCN 24611;
AstroSat CZTI detection: Ghumatkar et al., GCN 24613)
triggered Konus-Wind at T0=26732.082 s UT (07:25:32.082).

The burst light curve shows two pulses.
The first one starts at T0-39.0 s and ends at T0-3.7 s.
The second, bright, double-peaked pulse starts at T0-3.7 s and ends at 
T0+11.6 s.
The total duration of the burst is ~51 s.
The emission is seen up to ~1.5 MeV.

As observed by Konus-Wind, the burst
had a fluence of 3.20(-0.16,+0.18)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+6.752 s,
of 5.80(-1.01,+1.01)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the main pulse
(measured from T0 to T0+15.616 s)
is best fit in the 20 keV - 1.5 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.05(-0.09,+0.10),
and Ep = 125(-6,+7) keV (chi2 = 67/60 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -3.05 (chi2 = 67/59 dof).

The spectrum near the peak count rate
(measured from T0+0.256 to T0+7.424 s)
is best fit in the 20 keV - 1.5 MeV range
by the power law with exponential cutoff model
with  alpha = -0.93(-0.10,+0.10),
and Ep = 136(-6,+7) keV (chi2 = 65/60 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.96 (chi2 = 64/59 dof).

Modeling the K-W 3-channel spectrum of the initial pulse
(measured from T0-38.980 s to T0-3.652 s)
by a simple power law yields the photon index of 2.21(-0.07,+0.08),
chi2 = 0.94/1 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB190519_T26732/

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