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GCN Circular 24715

Konus-Wind observation of extremely bright GRB 190530A
2019-06-02T15:18:51Z (5 years ago)
Dmitry Frederiks at Ioffe Institute <>
D. Frederiks, S. Golenetskii, R.Aptekar, A. Kozlova,
A.Lysenko,  D. Svinkin, A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The extremely bright, long GRB 190530A
(Fermi GBM detection: GCN 24676,24692; AGILE-MCAL detection: GCN 24679;
Fermi-LAT detection: GCN 24679; AGILE/GRID analysis: GCN 24683;
AstroSat CZTI detection: GCN 24694) triggered Konus-Wind (KW)
at T0=37146.000 s UT (10:19:06.000).

The light curve of the burst shows a bright, multi-peaked pulse
with a total duration of ~55s, followed by a weaker and softer
emission tail visible until ~T0+150 s.
The emission in the bright phase of the burst is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at

As observed by Konus-Wind, the burst had
a fluence of (5.57 �� 0.15)x10^-4 erg/cm2 and
a 64-ms peak energy flux, measured from T0+14.912,
of (1.59 �� 0.10)x10^-4 erg/cm2 (both in the 20 keV - 10 MeV
energy range).

The time-integrated spectrum (measured from T0 to T0+44.228 s)
is best fit in the 20 keV - 16 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.03 (-0.02,+0.02),
the high energy photon index beta = -3.03 (-0.36,+0.22),
the peak energy Ep = 848 (-33,+44) keV,
chi2 = 140/96 dof.

The spectrum near the peak count rate (measured from T0+14.848 s
to T0+15.104 s) is best fit in the 20 keV - 16 MeV range
by a cutoff power-law (CPL) function with the following model
parameters: the photon index alpha = -0.41(-0.07,+0.07),
and the peak energy Ep = 1176(-46,+47) keV, chi2 = 55/60 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep, and an upper limit on beta of -3.2.

Assuming an upper limit on the burst redshift z<2.2 (Heintz et al.,
GCN 24686) and a standard cosmology with H_0 = 70 km/s/Mpc,
Omega_M = 0.30, and Omega_Lambda = 0.70, we estimate the following
upper limits on the GRB rest-frame energetics: the isotropic energy
release E_iso < 6.4x10^54 erg and the peak luminosity L_iso < 5.8x10^54
erg/s (both in the bolometric 1-10000 keV range).
Location of GRB 190530A in rest-frame hardness-intensity planes,
along with 'Amati' and 'Yonetoku' relations for the KW sample of
GRBs with known redshifts (Tsvetkova et al., ApJ 850 161, 2017), can be
found at

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
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