TITLE:   GCN CIRCULAR
NUMBER:  12358
SUBJECT: GRB 110915A: Konus-Wind and Swift/BAT joint spectral analysis
DATE:    11/09/19 21:22:41 GMT
FROM:    Valentin Pal'shin at Ioffe Inst  <val@mail.ioffe.ru>

V. Pal'shin, S. Golenetskii, R.Aptekar, E. Mazets, D. Frederiks, and
T. Cline on behalf of the Konus-Wind team,

T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC),
W. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), and T. Ukwatta (GWU)

report:

We performed the Konus-Wind and the Swift/BAT joint spectral analysis
of GRB 110915A (Swift/BAT trigger #503219: Holland et al., GCN Circ.
12335, Ukwatta et al. GCN Circ. 12352). Since the Konus-Wind observed
this GRB in the waiting mode, we only have 3 channel spectral data for
the Konus-Wind which cover the energy range from 20 keV to 1.2 MeV.  The
joint spectral analysis of the Konus-Wind and the Swift/BAT data
allows us to derive the broad-band spectral parameters of this burst.

The time interval of the spectral data for each instrument is chosen
from T0(BAT)-3.3 to T0(BAT)+82.1 s where T0(BAT) is the trigger time
of BAT at 13:20:44.40 UTC.  The energy ranges which we used in the joint
spectral analysis are 20-1200 keV and 14-150 keV for the Konus-Wind and
the Swift/BAT respectively.  The spectral data of two instruments are
fitted with the spectral model multiplied by the constant factor to take
into account the systematic effective area uncertainties in the response
matrices of each instrument.

The spectrum is well fitted with a power-law with exponential cutoff
model: dN/dE ~ E^{alpha}*exp(-(2+alpha)*E/Epeak). No systematic residual 
from the best fit model is seen in the spectral data of each instrument. 
The BAT constant factor is 0.76(-0.08,+0.09) (the KW constant factor is 
fixed to 1). The best fit spectral parameters are: alpha = -1.08 
(-0.14/+0.19) and Epeak = 183 (-48/+80) keV (chi2/dof = 62/58). The best 
fit spectral parameters for the GRB (Band) model are: alpha = 
-0.90(-0.21,+0.24), beta = -2.2(-0.8,+0.3), and Epeak = 132(-28,+57) keV 
(chi2/dof = 58/57). The derived alpha and Epeak are in agreement with 
those derived from analysis of the BAT data alone (Ukwatta et al. GCN 
Circ. 12352). The energy fluence in the 15-1200 keV band calculated by a 
power-law with exponential cutoff model for this 85.4 s interval is 
1.35(-0.20,+0.25)x10^-5 erg/cm2.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB110915A/

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