GCN Circular 9968

S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
P. Oleynik, M. Ulanov, and D. Svinkin on behalf of
the Konus-RF team, report:

The bright GRB 090929A (Fermi-GBM trigger trigger 275891585:
Rau, GCN 9962
Not found
 
 
) localized by Swift-BAT (Cummings and Krimm , GCN 9966
Not found
 
 
)
triggered Konus-RF at T0=16384.747 s UT (04:33:04.747).

The burst light curve shows several multipeaked pulses with a total
duration of ~6 s.

As observed by Konus-RF the burst
had a fluence of 1.24(-0.11, +0.12)x10^-5 erg/cm2,
and a 16-ms peak flux measured from T0-0.040 s
of (2.02 +/- 0.46)x10^-5 erg/cm2/s
(both in the 20 keV - 3 MeV energy range).

The time-integrated spectrum of the burst (from T0-1.2 to T0+4.5 s)
is well fitted (in the 10 keV - 3 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), with
alpha = -0.55(-0.11, +0.12),  and
Ep = 480(-54, +64) keV (chi2 = 120.1/119 dof).
The spectrum accumulated over the burst maximum (from T0-0.2 to T0+0.1 
s) is well fitted (in the 10 keV - 3 MeV range)
by a power law with exponential cutoff model with
alpha = -0.28(-0.14, +0.15),  and
Ep = 633(-71, +81) keV (chi2 = 44.0/56 dof).
Fitting by GRB (Band) model yields the same alpha and Ep,
and only an upper limit on the high energy
photon index: beta < -3.06 (chi2 = 44.0/55 dof).

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

The Konus-RF light curve of this GRB is available
at http://www.ioffe.ru/LEA/GRBs/GRB090929_T16384/KRF/