GCN Circular 21299
Subject
Konus-Wind observation of GRB 170705A
Date
2017-07-06T11:16:24Z (7 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik,
M. Ulanov, A. Tsvetkova, A. Lysenko, A.Kozlova, and T. Cline
on behalf of the Konus-Wind team, report:
The long-duration GRB 170705A
(Swift-BAT observation: Starling et al., GCN Circ. 21289;
Fermi-GBM observation: Bissaldi and Meegan, GCN Circ. 21297)
triggered Konus-Wind at T0=9956.188 s UT (02:45:56.188).
The burst light curve shows a bright, multipeaked pulse,
which starts at ~T0-6 s and has a total duration of ~25 s,
followed by a weaker emission seen up to ~T0+300 s.
The emission in the main episode is seen up to ~1 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170705_T09956/
As observed by Konus-Wind, the burst
had a fluence of 1.76(-0.19,+0.20)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+2.384 s,
of 4.21(-0.94,+0.96)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the main episode
(measured from T0 to T0+24.832 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.31(-0.17,+0.20)
and Ep = 155(-22,+31) keV (chi2 = 53/62 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.7
(chi2 = 59/61 dof).
The spectrum near the maximum count rate
(measured from T0+0.256 to T0+8.448 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
with alpha = -1.16(-0.15,+0.16)
and Ep = 166(-18,+23) keV (chi2 = 69/61 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3
(chi2 = 69/60 dof).
Assuming the redshift z=2.010 (de Ugarte Postigo et al.,
GCN Circ. 21298) and a standard cosmology model
with H_0 = 70 km/s/Mpc, Omega_M = 0.27, and Omega_Lambda = 0.73,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~1.8x10^53 erg,
the peak luminosity L_iso is ~1.3x10^53 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~466 keV.
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.