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GCN Circular 12276

Subject
GRB 110801A: Konus-Wind and Swift/BAT joint spectral analysis
Date
2011-08-15T15:05:55Z (13 years ago)
From
Takanori Sakamoto at NASA/GSFC <takanori@milkyway.gsfc.nasa.gov>
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), 
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), 
M. Stamatikos (OSU), J. Tueller (GSFC), and T. Ukwatta (MSU)

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

We performed the Konus-Wind and the Swift/BAT joint spectral analysis 
of GRB 110801A (Swift/BAT trigger #458521: De Pasquale et al., GCN Circ. 12228, 
Barthelmy et al. GCN Circ. 12237).  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 is chosen from T0(BAT)-26.43 to 
T0(BAT)+64.83 sec and from T0(BAT)+332.74 to T0(BAT)+388.67 sec where T0(BAT) 
is the trigger time of BAT at 19:49.43 UTC to include two time-separated episodes.  
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).  The constant factors of each 
instrument agree within 10%. No systematic residual from the best fit model is 
seen in the spectral data of each instrument (see Sakamoto et al. 2011, PASJ, 63, 
215 for the spectral cross-calibration).  The best fit spectral parameters are: 
alpha = -1.70 (-0.15/+0.12) and Epeak = 140 (-60/+900) keV (chi2/dof = 74/58).  
The best fit spectral parameters for the GRB (Band) model fixing beta = -2.5 are: 
alpha = -1.70 (-0.15/+0.22), and Epeak = 140 (-50/+1270) keV (chi2/dof = 74/58). 
The energy fluence in the 15-1200 keV band calculated by a power-law with 
exponential cutoff model for this 147.2 sec interval is 7.3 (-0.9/+ 1.7)x10^-6 erg/cm2.  

Assuming z=1.858 (Cabrera Lavers et al. GCN Circ. 12234) and a standard cosmology 
model with H_0 = 71 km/s/Mpc, Omega_M = 0.27, Omega_Lambda = 0.73, the isotropic 
energy release is E_iso = 1.0 (-0.2/+0.3) x10^53 erg in 1 keV to 10 MeV at the 
GRB rest frame extrapolating the best Band function fit fixing beta = -2.5. 

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

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB110801A/
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