[vsnet-grb-info 21781] Konus-Wind observation of GRB 190206A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23880
SUBJECT: Konus-Wind observation of GRB 190206A
DATE:    19/02/06 18:33:33 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova at mail.ioffe.ru>

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 extremely bright, short-duration, hard-spectrum
GRB 190206A (IPN triangulation: Svinkin et al., GCN Circ. 23879)
triggered Konus-Wind at T0=13763.926 s UT (03:49:23.926).

The burst light curve shows a single smooth pulse
which starts at ~T0 s and has a total duration of ~0.1 s.
There is no evidence of an extended emission following the burst.
The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst
had a fluence of 1.64(-0.17,+0.17)x10^-5 erg/cm2,
and a 16-ms peak flux, measured from T0+0.004 s,
of 6.44(-0.75,+0.76)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+0.064 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.58(-0.10,+0.12)
and Ep = 1600(-223,+248) keV (chi2 = 31/30 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.3
(chi2 = 30/29 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB190206_T13763/

The spectrum of the burst is typical of short-hard GRBs.
Assuming the measured fluxes, GRB 190206A is the third-brightest
short GRB detected by KW since November, 1994 in terms of peak flux,
and among the dozen brightest short GRBs, in terms of the fluence
(Svinkin et al. 2016, ApJS 224 10).

Although the redshift of GRB 190206A is not available (yet),
a comparison of the provisional track of the burst in the Ep,z-Eiso
and Ep,z-Liso planes with the KW sample of GRBs with known redshifts
(Tsvetkova et al., 2017, ApJ 850 161) suggests z < 0.5
(see http://www.ioffe.ru/LEA/GRBs/GRB190206_T13763/GRB190206A_z.pdf).

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