[vsnet-grb-info 3925] Konus-Wind observation of GRB 061021

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5748
SUBJECT: Konus-Wind observation of GRB 061021
DATE:    06/10/23 14:22:58 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 061021 (Swift-BAT trigger #234905:
Moretti et al., GCN 5743; Palmer et al., GCN 5744)
triggered Konus-Wind at T0=56348.304 s UT (15:39:08.304).

As observed by Konus-Wind the burst shows
a single pulse with a duration of ~10 s,
followed by a weak tail seen up to T-T0 ~60 s.

The spectrum of the pulse integrated from T0 to T0+8.448 s
is well fitted (in the 20 keV - 2 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha) * exp(-(2-alpha)*E/Ep)
with alpha = 1.22(-0.14, +0.12)
and Ep = 777 (-237, +549) keV (chi2 = 58/59 dof).
The fluence of this part is 9.93(-4.14, +0.69)x10^-6 erg/cm2
(in the 20 keV - 2 MeV range).

The spectrum of the tail integrated from T0+8.448 s to T0+57.600 s
can be fitted (in the 20 keV - 2 MeV range)
by a simple power law with the photon
index 1.93(-0.27, +0.32) (chi2 = 77/60 dof).
The fluence of this part is 3.43(-2.20, +0.83)x10^-6 erg/cm2
(in the 20 keV - 2 MeV range).
We note that because of the derived photon index is ~2,
this fluence value is very sensitive to the upper boundary
of the energy range.

The total burst fluence is 1.34(-0.47, +0.11)x10^-5 erg/cm2,
and the 256-ms peak flux measured from T0+0.608 s
3.72(-1.62, +0.53)x10^-6  erg/cm2/s
(both in the 20 keV - 2 MeV energy range).

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