TITLE:   GCN CIRCULAR
NUMBER:  20567
SUBJECT: Konus-Wind observation of GRB 170127C (short/hard GRB with extended emission)
DATE:    17/01/29 16:15:14 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

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

The short/hard GRB 170127C (Fermi-GBM detection: Bissaldi et al.,
GCN 20543; Fermi-LAT detection: Moretti et al., GCN 20544;
AGILE analysis: Ursi et al., GCN 20545;
AstroSat CZTI Sharma:  Verrecchia et al., GCN 20561;
POLAR observation: Marcinkowski et al., GCN 20563)
triggered Konus-Wind at T0=5744.660 s UT (01:35:44.660).

The light curve shows a bright, hard initial pulse with a
duration of ~0.170 ms, followed, after a short period of quiescence,
by a weaker and softer emission episode lasing for ~16 s.
Even more weaker and softer emission is traced in the KW light curve
up to ~T0+90 s.
The emission in the initial pulse is seen up to ~5 MeV.

As observed by Konus-Wind, the burst had a total fluence of
1.62(-0.25, +0.49)x10^-5 erg/cm2 and a 16-ms peak energy flux,
measured from T0, of (1.1 ± 0.1)x10^-4 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the initial pulse
(measured from T0 to T0+0.192 s)
is best fit in the 20 keV - 15 MeV range
by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.01 (-0.14,+0.16), Ep = 887 (-88,+90) keV,
chi2 = 46/55 dof.

The time-averaged spectrum of the extended emission
(measured from T0+0.256 to T0+16.640 s)
is best fit in the 20 keV - 15 MeV range
by the CPL model with alpha = -1.19 (-0.29,+0.35),
Ep = 307 (-98,+342) keV, chi2 = 91/98 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170127_T05744/

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