[vsnet-grb-info 15937] Konus-Wind observation of GRB 141222A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17225
SUBJECT: Konus-Wind observation of GRB 141222A
DATE:    14/12/23 16:53:34 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, hard-spectrum, very intense GRB 141222A
(Fermi-LAT detection: McEnery et al., GCN Circ. 17218;
IPN triangulation: Golenetskii et al., GCN Circ. 17223)
triggered Konus-Wind at T0=25735.342 s UT (07:08:55.342).

The burst light curve starts with a short bright pulse with negligible 
spectral lag followed by two broader, less intense, pulses. The total 
burst duration is about 3.2 s. The emission is seen up to 5 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB141222_T25735/
The background variations in the soft KW band are due to solar activity.

As observed by Konus-Wind, the burst
had a fluence of 1.1(-0.2,+0.4)x10^-5 erg/cm2,
and a 16-ms peak flux, measured from T0+0.038 s,
of 1.2(-0.3,+0.3)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 5 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.50 (-0.10,+0.12)
and Ep = 858 (-375,+1067) keV (chi2 = 89/79 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -1.9
(chi2 = 89/78 dof).

The spectrum near the maximum count rate
(measured from T0 to T0+0.064 s)
is best fit in the 20 keV - 5 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.78 (-0.15,+0.17)
and Ep = 1532 (-359,+493) keV (chi2 = 25/29 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 = 25/28 dof).

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