[vsnet-grb-info 17083] Konus-Wind observation of GRB 151001B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18401
SUBJECT: Konus-Wind observation of GRB 151001B
DATE:    15/10/06 11:18:10 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova at mail.ioffe.ru>

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

At ~16 minutes before the Swift-BAT trigger on GRB 151001B
(Krimm, et al., GCN Circ. 18374; T0(BAT)=18:29:36 UT)
Konus-Wind detected, in the waiting mode, a burst of high X-ray/soft
gamma-ray emission which had a duration of ~191 s.

Taking into account the proximity of this burst to the Swift-BAT trigger
and consistency of the KW ecliptic latitude response with the position
of GRB 151001B we suggest this burst is the main part of GRB 151001B.

The K-W light curve of this burst is available at
http://www.ioffe.ru/LEA/GRBs/GRB151001B/
The count rate increase in the soft KW energy band, which follows the
burst from T0(BAT)-838 s to T0(BAT)+2488 s, can not be unambiguously
attributed to GRB 151001B.

As observed by Konus-Wind, the burst had a fluence of
8.5(-2.3,+0.6)x10^-6 erg/cm2 and a 2.944-s peak flux,
measured from ~T0(BAT)-1007.1 s, of 1.8(-0.6,+0.4)x10^-7 erg/cm2/s
(both in the 20 - 1000 keV energy range).

Modeling the K-W 3-channel time-integrated spectrum
(from T0(BAT)-1018.9 s to T0(BAT)-827.5 s)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -0.9(-0.3,+0.5) and Ep = 179 (-52,+75) keV.

All the quoted errors are at 1 sigma confidence level.
All the quoted values are preliminary.