GCN Circular 23637

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�� GRB 190106A (Swift detection: Sonbas et al., GCN 23615
Not found
 
 
;
Palmer et al., GCN 23625
Not found
 
 
)
triggered Konus-Wind at T0=48887.602 s UT (13:34:47.602).

The burst light curve shows a multi-peaked structure
which starts at ~T0-5 s and has a total duration of ~79 s.
The emission is seen up to ~2 MeV.

As observed by Konus-Wind, the burst
had a fluence of 1.12(-0.17,+0.25)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0-0.044 s,
of 1.81(-0.89,+1.19)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+82.176 s)
is best fit in the 20 keV - 16 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with�� alpha = -1.00(-0.50,+0.63),
and Ep = 171(-42,+90) keV (chi2 = 81/98 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.31 (chi2 = 81/97 dof).

The spectrum near the peak count rate
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 1.2 MeV range
by the power law with exponential cutoff model:
with�� alpha = -1.15(-0.50,+0.66),
and Ep = 216(-66,+308) keV (chi2 = 55/60 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -1.85 (chi2 = 55/59 dof).

Assuming the redshift z=1.859 (Xu et al., GCN 23629
Not found
 
 
;
Mao et al., GCN 23630
Not found
 
 
; Schady et al., GCN 23632
Not found
 
 
)
and a standard cosmology model with H_0 = 67.3 km/s/Mpc,
Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is 9.96(-1.55,+2.25)x10^52 erg,
the peak luminosity L_iso is 4.62(-2.28,+3.03)x10^52 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is 489(-120,+257) keV, and the rest-frame peak energy of
the 'peak' spectrum, Ep,p,z, is 618(-189, 881) keV.
With these energetics, the burst lies within the 68% prediction bands
for both 'Amati' and 'Yonetoku' relations built for the sample
of 138 long KW GRBs with known redshifts
(Tsvetkova et al., ApJ 850 161, 2017).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB190106_T48887/

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