[vsnet-grb-info 16222] Konus-Wind observation of GRB 150220A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17503
SUBJECT: Konus-Wind observation of GRB 150220A
DATE:    15/02/24 15:34:07 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin at mail.ioffe.ru>

S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 150220A (IPN triangulation: Hurley et al., GCN 
Circ. 17502) triggered Konus-Wind at T0=51704.661 s UT (14:21:44.661).

The burst light curve shows two emission episodes separated by ~100 s
with a total duration of ~160 s.
The emission is seen up to ~2 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150220_T51704/

As observed by Konus-Wind, the burst
had a fluence of 3.00(-0.29,+0.37)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+13.568 s,
of 4.61(-1.05,+1.07)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+147.712 s)
is best fit in the 20 keV - 3 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.86(-0.29,+0.34)
and Ep = 211(-34,+55) keV (chi2 = 49/64 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.2
(chi2 = 48/63 dof)

The spectrum near the maximum count rate
(measured from T0+8.448 to T0+16.640 s)
is best fit in the 20 keV - 3 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.98(-0.17,+0.19)
and Ep = 225(-28,+38) keV (chi2 = 54/64 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.6
(chi2 = 55/63 dof)

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