[vsnet-grb-info 17445] Konus-Wind observation of GRB 160104B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18869
SUBJECT: Konus-Wind observation of GRB 160104B
DATE:    16/01/15 09:48:49 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova 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:

GRB 160104B, localized by MAXI/GSC (Kawakubo et al., GCN 18818)
was detected by Konus-Wind in the waiting mode.

The K-W light curve shows two distinct emission episodes.
The first one, from ~T0(MAXI)-25.9 s to ~T0(MAXI)+6.5 s,
corresponds to the MAXI trigger(T0(MAXI)=10:13:06.662 UT).
The second episode is separated from the first one by ~500 s
and lasts for ~165 s, from ~T0(MAXI)+515.8 s to ~T0(MAXI)+680.7 s.

The K-W ecliptic latitude response in both episodes is consistent
with the position of GRB 160104B. Taking this into account,
we suggest that both episodes observed by K-W belong to GRB 160104B
and the total duration of the burst is ~710 s.

The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB160104B/

As observed by Konus-Wind, the first episode had a fluence of
6.64(-0.81,+0.87)x10^-6 erg/cm2 and a 2.944-s peak flux,
measured from ~T0(MAXI)-22.915 s, of 5.23(-0.88,+0.92)x10^-7 erg/cm2/s
(both in the 20 - 1200 keV energy range). The second episode had a
fluence of 1.36(-0.17,+0.17)x10^-5 erg/cm2 and a 2.944-s peak flux,
measured from ~T0(MAXI)+615.933 s, of 3.59(-0.75,+0.75)x10^-7 erg/cm2/s
(both estimated in the same energy range).

Fitting the K-W 3-channel time-integrated spectrum of the first episode
(from ~T0(MAXI)-25.9 s to ~T0(MAXI)+6.5 s)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -0.8(-0.2,+0.3) and Ep = 489 (-114,+195) keV.

Fitting the K-W 3-channel time-integrated spectrum of the second episode
(from ~T0(MAXI)+515.8 s to ~T0(MAXI)+680.7 s)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.4(-0.2,+0.2) and Ep = 481 (-175,+580) keV.

All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.