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GCN Circular 20995

Subject
Konus-Wind observation of GRB 170405A
Date
2017-04-06T14:57:40Z (7 years ago)
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 long GRB 170405A (Swift-BAT detection: Troja et al.,GCN 20984;
Fermi-GBM detection: Hui & Meegan., GCN 20986;
Fermi-LAT detection: Vianello & Kocevski, GCN 20987)
triggered Konus-Wind at T0=67181.254 s UT (18:39:41.254)

The light curve shows a multi-peaked structure
with a total duration of ~100 s and a hint of a subsequent
weak/soft emission lasting until ~T0+200 s.
The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst had a fluence of
(1.05 �� 0.12)x10^-4 erg/cm2 and a 64-ms peak energy flux,
measured from T0+15.744, of (5.9 �� 0.9)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+73.984 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 = -0.53 (-0.17,+0.19),
the high energy photon index beta = -2.36 (-0.25,+0.15),
the peak energy Ep = 244 (-27,+32) keV,
chi2 = 98/96 dof.

The spectrum near the peak count rate (measured from T0+8.448 s
to T0+24.832 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 = -0.54 (-0.22,+0.24),
the high energy photon index beta = -2.56 (-1.02,+0.27),
the peak energy Ep = 265 (-36,+51) keV,
chi2 = 71/96 dof.

Assuming the redshift z=3.510 (de Ugarte Postigo et al., GCN 20990)
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 ~2.6x10^54 erg,
the peak luminosity L_iso is ~6.6x10^53 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~1100 keV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170405_T67181/

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

[GCN OPS NOTE(06apr17):  Per author's request, in the first paragraph
the V&K CirNum was changed from "20827" to "20987",  and in the 6th paragraph
the de Ugarte Postigo CircNum was changed from "20104" to "20990".]
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