[vsnet-grb-info 14929] Konus-Wind observation of GRB 140506A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16223
SUBJECT: Konus-Wind observation of GRB 140506A
DATE:    14/05/08 13:33:01 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lyssenko, and T. Cline
on behalf of the Konus-Wind team, report:

A long-duration GRB 140506A (Swift-BAT trigger 598284:
Gompertz et al., GCN 16214; Markwardt et al., GCN 16218;
Fermi-GBM detection: Jenke, GCN 16220)
triggered Konus-Wind at T0=76059.098 s UT (21:07:39.098).

The light curve shows two bursting episodes: a narrow,
double-peaked pulse from ~T0-1.1 s to ~T0+1.6 s,
followed by a broad, weak, soft pulse from ~T0+49 s to ~T0+63 s
A total duration of the burst is ~64 s.
The emission is seen up to ~7 MeV.

As observed by Konus-Wind, the burst had a fluence
of 6.6(-1.6,+1.8)x10^-6 erg/cm2, and a 64-ms peak flux,
measured from T0+0.640 s, of 6.2(-1.9,+2.5)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the first bursting episode
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 18 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.3 (-0.2,+0.3),
the high energy photon index beta = -2.3 (-7.7,+0.4),
the peak energy Ep = 187 (-59,+90) keV,
chi2 = 94/97 dof.

The time-averaged spectrum of the second bursting episode
(measured from T0+49.408 to T0+65.792 s)
is best fit in the 20 keV - 18 MeV range
by a simple power-law function with
the photon index 2.06(-0.13,+0.14),
chi2 = 98/98 dof.

Assuming the redshift z=0.889 (Fynbo et al., GCN 16217)
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 ~1.4x10^52 erg,
the peak luminosity L_iso is ~2.5x10^52 erg/s,
and the rest-frame peak energy, Ep,i, is ~350 keV
(as derived from the spectrum of the first episode).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB140506_T76059/

All the quoted errors are at the 1 sigma confidence level.
All the quoted values are preliminary.