TITLE:   GCN CIRCULAR
NUMBER:  6124
SUBJECT: Konus-Wind and Konus-A observations of GRB 070220
DATE:    07/02/21 14:46:52 GMT
FROM:    Valentin Pal'shin at Ioffe Inst  <val@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 070220 (Swift-BAT trigger #261299:
Stamatikos et al., GCN 6114; Parsons et al., GCN 6121)
triggered Konus-Wind at T0=17076.976 s UT (04:44:36.976).
Konus-A observed GRB 070220 in the waiting mode.

The Konus-Wind light curve shows a multipeaked pulse
with a long decaying tail clearly seen up to T-T0 ~130 sec
in both G1(18-70 keV) and G2(70-300 keV) bands.
So, the Swift XRT and UVOT were on target and begun
observations during the hard prompt emission
(Stamatikos et al., GCN 6114; Beardmore et al., GCN 6118;
M. De Pasquale and M. Stamatikos 6120).

As observed by Konus-Wind the burst had a
fluence of (2.98 +/- 1.15)x10^-5 erg/cm2,
and the 256-ms peak flux measured from T0+9.600 s
(2.47 +/- 0.50)x10^-6  erg/cm2/s
(both in the 20 keV - 2 MeV energy range).

The time-integrated spectrum of the GRB
(from T0 to T0+123.136 s) is well fitted (in the 20 keV - 2 MeV range)
by GRBM (Band) model for which:
the low-energy photon index is alpha =  -1.21 (-0.19, +0.29),
the high energy photon index beta = -2.02 (-0.44, +0.27),
the peak energy Ep = 299 (-130, +204) keV (chi2 = 52/60 dof).
Fitting by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha) * exp(-(2-alpha)*E/Ep)
yields alpha = 1.33(-0.18, +0.15)
and Ep = 443(-150, +420) keV (chi2 = 55/61 dof).

The spectrum of the burst maximum
(accumulated from T0 s to T0+16.640 s)
is well fitted
(in the 20 keV - 2 MeV range)
by GRBM (Band) model for which:
the low-energy photon index is alpha = -1.04 (-0.15, 0.18),
the high energy photon index beta = -2.07 (-0.36, 0.18),
the peak energy Ep = 261 (-57, +81) keV (chi2 = 59/60 dof).
The fluence of this part is 1.62(-0.20, +0.19)x10^-5 erg/cm2.

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/GRB070220_T17076/