TITLE:   GCN CIRCULAR
NUMBER:  16621
SUBJECT: Konus-Wind observation of GRB 140721A
DATE:    14/07/23 10:30:26 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@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:

The long-duration GRB 140721A (Fermi-GBM detection: Yu, GCN 16617;
IPN triangulation: Hurley et al., GCN 16620)
triggered Konus-Wind at T0=29009.138 s UT (08:03:29.138).

The light curve shows a multi-peaked structure which
started ~60 s before the trigger.
A total duration of the burst is ~160 s.
The emission is seen up to 5 MeV.

As observed by Konus-Wind, the burst had a fluence
of 4.7(-0.4,+0.4)x10^-5 erg/cm2, and a 64-ms peak flux,
measured from T0+10.496 s, of 5.0(-0.5,+0.5)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+98.560 s)
is best fit in the 20 keV - 10 MeV range
by the cutoff power law with the following model parameters:
the photon index alpha = -1.31(-0.11,+0.12),
and the peak energy Ep = 153(-15,+19) keV,
chi2 = 65/85 dof.
Fitting this spectrum with the Band model yields the same
values of alpha and Ep with an upper limit on beta of -2.5

The spectrum near the peak count rate (measured from T0 to T0+16.640 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 = -0.94 (-0.20,+0.24),
the high energy photon index beta = -2.15 (-0.24,+0.13),
the peak energy Ep = 166 (-29,+44) keV,
chi2 = 60/87 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB140721_T29009/

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