[vsnet-grb-info 19916] Konus-Wind observation of GRB 171010A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22003
SUBJECT: Konus-Wind observation of GRB 171010A
DATE:    17/10/12 11:50:56 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, very bright GRB 170409A (Fermi-LAT detection: Omodei et al.,
GCN 21985; Fermi-GBM detection: Poolakkil and Meegan, GCN 21992)
triggered Konus-Wind at T0=68460.142 s UT (19:01:00.142)

The burst light curve shows a bright, multi-peaked pulse,
with a total duration of ~155 s (from ~T0-8 s -- ~T0+147 s),
which was preceded by a weaker emission starting from ~T0-150 s.
A much weaker pulse is also seen in the KW light curve around ~T0+250 s.
The emission is seen up to ~15 MeV.

As observed by Konus-Wind, the burst had a fluence of
(6.5 ± 0.2)x10^-4 erg/cm2 and a 64-ms peak energy flux,
measured from T0+26.496, of (2.45 ± 0.17)x10^-5 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+147.968 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.09 (-0.04,+0.04),
the high energy photon index beta = -2.42 (-0.07,+0.06),
the peak energy Ep = 171 (-6,+7) keV,
chi2 = 95/95 dof.

The spectrum near the peak count rate (measured from T0+26.112 s
to T0+27.136 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.75 (-0.06,+0.06),
the high energy photon index beta = -2.58 (-0.22,+0.16),
the peak energy Ep = 273 (-27,+27) keV,
chi2 = 78/70 dof.

Assuming the redshift z=0.33 (Kankare et al., GCN 22002)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.3, and Omega_Lambda = 0.7,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~1.8x10^53 erg,
the peak luminosity L_iso is ~8.8x10^51 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~227 keV.


The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB171010_T68460/

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