[vsnet-grb-info 16081] Konus-Wind observation of GRB 150127B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17363
SUBJECT: Konus-Wind observation of GRB 150127B
DATE:    15/01/30 14:03:07 GMT
FROM:    Valentin Pal'shin at Ioffe Inst  <val 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 150127B (IPN triangulation: Hurley et al., GCN 
17360) triggered Konus-Wind at T0=50911.89 s UT (14:08:31.890).

The burst light curve shows two multi-peak emission episodes with a 
total duration of ~90 s.
The emission is seen up to ~1 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150127_T50911/

As observed by Konus-Wind, the burst
had a fluence of 5.43(-0.21,+0.23)x10^-5 erg/cm2,
and a 256-ms peak flux, measured from T0+10.288 s,
of 2.97(-0.43,+0.43)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+82.176 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.98(-0.10,+0.10)
and Ep = 197(-12,+14) keV (chi2 = 40/58 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.8
(chi2 = 40/57 dof)

The spectrum near the maximum count rate
(measured from T0+0.000 to T0+16.640 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.23(-0.13,+0.14)
and Ep = 252(-13,+14) keV (chi2 = 49/58 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.9
(chi2 = 47/57 dof)

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