GCN Circular 8101
Subject
GRB 080810: Konus-Wind and Swift/BAT joint spectral analysis
Date
2008-08-12T21:24:11Z (17 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), 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).
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). 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; Burenin et al.,
GCN Circ. 8088) 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.