GCN Circular 16234

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:

The long-duration, very intense GRB 140508A
(Fermi-GBM detection: Yu and Goldstein, GCN 16224
Not found
 
 
;
IPN triangulation: Hurley et al., GCN 16225
Not found
 
 
)
triggered Konus-Wind at T0=11038.423 s UT (03:03:58.423).

The light curve shows multiple emission episodes with decaying
peak intensity. A total duration of the burst is ~80 s.
The emission is seen up to ~9 MeV.

A hint of an extended emission in softer energy channels
can be traced to at least 250 s after the trigger; however,
its attribution to GRB 140508A is unclear due to the variable
solar particle background.

As observed by Konus-Wind, the burst had a fluence
of 7.4(-0.7,+0.8)x10^-5 erg/cm2, and a 64-ms peak flux,
measured from T0+2.576 s, of 3.0(-0.2,+0.2)x10^-5 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+72.448 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.11 (-0.08,+0.09),
the high energy photon index beta = -2.5 (-0.4,+0.2),
the peak energy Ep = 213 (-20,+23) keV,
chi2 = 70/86 dof.

The spectrum near the peak count rate (measured from T0 to T0+4.864 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.0 (-0.1,+0.1),
the high energy photon index beta = -2.4 (-0.2,+0.1),
the peak energy Ep = 345 (-47,+59) keV,
chi2 = 65/64 dof.

Assuming the redshift z=1.03 (Malesani et al., GCN 16229
Not found
 
 
;
Wiersema et al., GCN 16231
Not found
 
 
)
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 ~2.1x10^53 erg,
the peak luminosity L_iso is ~1.8x10^53 erg/s,
and the rest-frame peak energy, Ep,i, is ~430 keV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB140508_T11038/

All the quoted errors are at the 90% sigma confidence level.
All the quoted values are preliminary.