[vsnet-grb-info 19965] Konus-Wind observation of GRB 171022A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22052
SUBJECT: Konus-Wind observation of GRB 171022A
DATE:    17/10/26 18:49:24 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at 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 long GRB 171022A (Fermi-LAT detection: Palatiello et al.,
GCN 22045; Fermi-GBM detection: Hamburg and Meegan, GCN 22046;
IPN Triangulation: Hurley et al., GCN 22051)
triggered Konus-Wind at T0=76456.523 s UT (21:14:16.523).

The KW light curve shows a multi-peaked emission complex
with a total duration of ~15 s. A much weaker pulse is also
seen in the softest KW light curve around ~T0+215 s.
The emission is seen up to ~3.5 MeV.

As observed by Konus-Wind, the burst had a fluence of
(7.1 ± 0.7)x10^-6 erg/cm2 and a 64-ms peak energy flux,
measured from T0+3.328, of (2.4 ± 0.2)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+16.640 s)
is best fit in the 20 keV - 15 MeV range by a cutoff power-law
(CPL) function with the following model parameters:
the photon index alpha = -0.51(-0.30,+0.34),
and the peak energy Ep = 144(-13,+17) keV,
chi2 = 93/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep, and an upper limit on beta of -2.7,
chi2 = 93/97 dof.

The spectrum near the peak count rate (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range by the CPL function
with the following model parameters:
the photon index alpha = -0.40(-0.27,+0.30),
and the peak energy Ep = 146(-12,+14) keV,
chi2 = 111/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep, and an upper limit on beta of -2.8,
chi2 = 110/97 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB171022_T76456/

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