GCN Circular 8101

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), K. McLean (GSFC/UMD), 
D. Palmer (LANL), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), 
J. Tueller (GSFC), and T. Ukwatta (GWU) 
on behalf of the Swift-BAT team:  

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

Report:

We performed the Konus-Wind and the Swift/BAT joint spectral analysis 
of GRB 080810 (Swift/BAT trigger #319584; Page et al., GCN Circ. 8080
Not found
 
 
).  
Since the Konus-Wind observed this GRB in the waiting mode, we only 
have 3 channel spectral data for the Konus-Wind.  However, the 
Konus-Wind data covers the energy range from 20 keV to 1 MeV.  Therefore, 
the joint spectral analysis of the Konus-Wind and the Swift/BAT data 
enables 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)-18.6 to T0(BAT)+60.8 sec where T0(BAT) is the trigger time of BAT 
at 13:10:12.3 UTC.  This time interval includes most of the burst emission, 
but not the last pulse around T0(BAT)+~100 sec which is clearly visible in 
the BAT data (Sakamoto et al., GCN Circ. 8082
Not found
 
 
).  The energy ranges which we 
used in the joint spectral analysis are 20-1000 keV and 14-150 keV for 
the Konus-Wind and the Swift/BAT respectively.  The spectral data of two 
instruments are fit with the spectral model multiplied by the constant factor 
to take into account the systematic uncertainties in the response matrices 
of each instrument.

The spectrum is well fit 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 20%.  No systematic residual from the best fit model 
is seen in the spectral data of each instrument.  The best fit spectral 
parameters are: alpha = -1.2 +- 0.1 and Epeak = 550 (-230/+860) keV 
(chi2/dof = 41/58).  The best fit spectral parameters for the Band function 
fixing beta=-2.5 are: alpha = -1.2 +- 0.1 and Epeak = 580 (-260/+850) keV 
(chi2/dof = 41/58).  The energy fluence in the 15-1000 keV band calculated 
by a power-law with exponential cutoff model for this 79.5 sec interval is 1.7 
(-0.2/+0.1) x 10^-5 erg/cm2 (assuming the constant factor of the BAT is fixed to 1).  

Assuming z = 3.35 (Prochaska et al., GCN Circ. 8083
Not found
 
 
; Burenin et al., 
GCN Circ. 8088
Not found
 
 
) 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 ~5 x 10^53 erg in 1 keV to 10 MeV at the GRB rest frame extrapolating 
the best fit model spectrum.  

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