GCN Circular 21859
Subject
Konus-Wind observation of GRB 170906A
Date
2017-09-11T16:11:07Z (7 years ago)
From
Anastasia Tsvetkova at Ioffe Institute <tsvetkova@mail.ioffe.ru>
A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik,
M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline
on behalf of the Konus-Wind team, report:
The long-duration GRB 170906A (Swift-BAT trigger #770957:
Siegel et al., GCN 21821; Cummings et al., GCN 21838;
Fermi-LAT detection: Bissaldi et al., GCN 21827;
Fermi GBM detection: Hamburg & Meegan, GCN 21839;
AstroSat CZTI(Veto) detection: Sharma et al., GCN 21856)
triggered Konus-Wind at T0=2607.999 s UT (00:43:27.999).
The burst light curve shows a double-peaked structure
started at ~T0-23 s with a total duration of ~91 s,
followed by a weaker emission seen up to ~T0+135 s.
The KW data above 1.5 MeV are largely contaminated
by high solar particle background.
As observed by Konus-Wind, the burst
had a fluence of 1.19(-0.21,+0.22)x10^-4 erg/cm2,
and a 64-ms peak energy flux, measured from T0+11.184 s,
of 9.25(-2.67,+2.97)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+68.608 s)
is best fit in the 20 keV - 1.5 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.91(-0.10,+0.12),
the high energy photon index beta = -2.41(-0.94,+0.28),
the peak energy Ep = 274(-37,+43) keV,
chi2 = 86/59 dof.
The spectrum near the peak count rate
(measured from T0+6.400 to T0+16.384 s)
is best fit in the 20 keV - 1.5 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.60(-0.12,+0.15),
the high energy photon index beta = -2.36(-0.75,+0.31),
the peak energy Ep = 360(-54,+58) keV,
chi2 = 64/59 dof.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170906_T02607/
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.