[vsnet-grb-info 4712] Konus-Wind observation of GRB 070521

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6459
SUBJECT: Konus-Wind observation of GRB 070521
DATE:    07/05/23 16:45:59 GMT
FROM:    Valentin Pal'shin at Ioffe Inst  <val at mail.ioffe.ru>

S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
and T. Cline on behalf of the Konus-Wind team report:

The long GRB 070521 (Swift-BAT trigger #279935:
Guidorzi et al., GCN 6431; Palmer et al., GCN 6440) triggered
Konus-Wind at T0=24691.587 s UT (06:51:31.587).

The burst started at T-T0 ~-33 s and had a duration of ~55 s.
As observed by Konus-Wind the burst
had a fluence of 1.81(-0.31, +0.06)x10^-5 erg/cm2,
and a 64-ms peak flux measured from T0+5.312 s
4.12(-1.07, +0.78)x10^-6 erg/cm2/s
(both in the 20 keV - 1 MeV energy range).
The burst shows strong spectral evolution.

The time-integrated spectrum of the burst
(from T0 to T0+23.808 s: this interval comprises ~80%
of the burst total counts) can be fitted
(in the 20 keV - 1 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep)
with alpha = 0.93 +/- 0.12
and Ep = 222(-21, +27) keV (chi2 = 43/56 dof).

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

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB070521_T24691/