Spectral analysis of a precursor peak in SGR1806-02 (ver2.0)

M.Suzuki, T. Sakamoto and G.Sato 15/Jan/2005

Here is 2nd report which is a spectral analysis of the precursor event (T-140sec) with a rich response.

(1) The 10 times rich statistics response matrix for SGR1806-20

Figure.1: Response matrix images
The Input Energy vs. Output Energy. Left side is old response matrix image and Right side is new one.

Figure.2: Effective area
The effective area is showed by Xspec command, "plot eff".

(2) Fitting result

Figure.4: Spectrum fitting

This spectrum is well modeled by bremsstrahlung. The temperature obtaines kT = 20.6 keV (old values is 26.5 keV). I compare the old fitting parameters and new ones as follow.

Old

Model: bremss<1>

---------------------------------------------------------------------------
---------------------------------------------------------------------------
Model:  bremss<1>
Model Fit Model Component  Parameter  Unit     Value
par   par comp
  1    1    1   bremss     kT       keV        26.5043     +/-  0.116759
  2    2    1   bremss     norm                89365.8     +/-   1665.03
---------------------------------------------------------------------------
---------------------------------------------------------------------------
Chi-Squared =      3107.087     using    73 PHA bins.
Reduced chi-squared =      43.76178     for     71 degrees of freedom
Null hypothesis probability =  0.00
XSPEC>flux 20 194.9
Model flux   6205.     photons ( 3.4131E-04 ergs)cm**-2 s**-1 ( 20.000-194.900)

New

Model: bremss<1>

---------------------------------------------------------------------------
---------------------------------------------------------------------------
Model:  bremss<1>
Model Fit Model Component  Parameter  Unit     Value
par   par comp
  1    1    1   bremss     kT       keV        20.6080     +/-  0.528929E-01
  2    2    1   bremss     norm                238957.     +/-   2161.66
---------------------------------------------------------------------------
---------------------------------------------------------------------------
Chi-Squared =      849.6900     using    71 PHA bins.
Reduced chi-squared =      12.31435     for     69 degrees of freedom
Null hypothesis probability =  0.00
XSPEC>flux 20 194.9
Model flux  1.1956E+04 photons ( 6.1277E-04 ergs)cm**-2 s**-1 ( 20.000-194.900)

Isotropic emission (Assuming a distance of ~15 kpc):

Old: ~1.4x10^43 erg
New: ~2.5x10^43 erg

Data

XSPEC LOG File(ver2.0)