GCN Circular 11692
Subject
GRB 110205A: Swift/BAT and Suzaku/WAM joint spectral analysis
Date
2011-02-10T18:55:44Z (13 years ago)
From
Takanori Sakamoto at NASA/GSFC <Taka.Sakamoto@nasa.gov>
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
S. Sugita (Nagoya U.), K. Yamaoka (Aoyama Gakuin U.), N. Vasquez (Tokyo Tech.),
T. Uehara, Y. Hanabata, T. Takahashi, Y. Fukazawa (Hiroshima U.),
Y. Terada, M. Tashiro, W. Iwakiri, K. Takahara, T. Yasuda (Saitama U.),
M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA),
Y. E. Nakagawa, T. Tamagawa (RIKEN), N. Ohmori, A. Daikyuji, Y. Nishioka,
M. Yamauchi (Univ. of Miyazaki), Y. Urata, P. Tsai (NCU),
K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Hong (Nihon U.)
(i.e. the Suzaku WAM team):
We performed the Swift/BAT and the Suzaku/WAM joint spectral analysis
of GRB 110205A (Swift/BAT trigger #444643: Beardmore et al., GCN Circ.
11629, Markwardt et al. GCN Circ. 11646). The joint spectral analysis
of the Swift/BAT and the Suzaku/WAM 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)+20.2 to T0(BAT)+318.2 sec where T0(BAT) is the trigger time
of BAT at 02:02:41.3 UTC. The energy ranges which we used in the joint
spectral analysis are 15-150 keV and 100-3000 keV for the Swift/BAT and
the Suzaku/WAM 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. The
best fit spectral parameters are: alpha = -1.59 (-0.06/+0.07) and Epeak
= 230 (-65/+135) keV (chi2/dof = 96.6/85). A simple power-law fit
shows a poor fit to the data (chi2/dof=126.4/86). The best fit spectral
parameters for the Band function fixing beta = -2.5 are:
alpha = -1.57 (-0.08/+0.10), and Epeak = 200 (-60/+130) keV (chi2/dof = 96.9/85).
Our best fit spectral parameters are consistent with the Konus-Wind
result based on the 3 channel data (Golenetskii et al. GCN Circ. 11659).
The energy fluence in the 15-3000 keV band calculated by a power-law with
exponential cutoff model for this 298 sec interval is 2.7 (-0.4/+0.7)x10^-5 erg/cm2.
Assuming z = 2.22 (Cenko et al. GCN Circ. 11638; Vreeswijk et al. GCN Circ. 11640)
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 = 4.6 (-0.7/+0.4) x10^53 erg in 1 keV to 10 MeV at the GRB rest frame.
All the quoted errors are at the 90% confidence level.