[vsnet-grb-info 17389] Konus-Wind observation of GRB 151227B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18781
SUBJECT: Konus-Wind observation of GRB 151227B
DATE:    15/12/31 08:50:48 GMT
FROM:    Anastasia Tsvetkova at Ioffe Institute  <tsvetkova at mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik, M. Ulanov,
D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration, intense GRB 151227B
(Fermi GBM detection: Toelge & Bissaldi, GCN 18727;
IPN Triangulation: Hurley et al., GCN 18773)
triggered Konus-Wind at T0=18827.479 s UT (05:13:47.479).

The burst light curve shows three emission episodes with a total 
duration of ~48 s.
The emission is seen up to ~15 MeV.

As observed by Konus-Wind, the burst
had a fluence of 6.49(-0.72,+0.72)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+29.728 s,
of 1.11(-0.20,+0.19)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+43.776 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.19(-0.08,+0.10),
the high energy photon index beta = -2.11(-0.18,+0.11),
the peak energy Ep = 228(-40,+46) keV,
chi2 = 110/97 dof.

The spectrum near the peak count rate
(measured from T0+24.832 to T0+35.584 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.25(-0.05,+0.05),
the high energy photon index beta = -2.57(-1.09,+0.28),
the peak energy Ep = 353(-44,+52) keV,
chi2 = 111/93 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB151227_T18827/

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