\begin{table}%t2
\caption{Best-fit spectral parameters of the log-parabolic model for the XRT 
(first section) and \sax\ (second section) observations of \pks.}
\label{tab2}
\small%\centerline
{
\begin{tabular}{llcccccc}
\hline
\hline
 & & & & & & & \\[-8pt]
Instrument& Date     & $K^{(1)}$  & $a^{(1)}$ & $b^{(1)}$ & $E_{\rm p}$ & $F_{2-10}^{(2)}$ & $\chi^2_{\rm r}$/d.o.f.  \\[2mm]
   &  &  & &  & (keV) & (erg cm$^{-2}$ s$^{-1}$) &  \\
\hline
 & & & & & & & \\[-8pt]
\swift\ XRT & 2005 April 26 & 1.41 (0.05)~$\times$ 10$^{-2}$ & 1.81 (0.07) & 0.18 (0.13) & 3.4  &
4.0 $\times$ 10$^{-11}$ & 0.75/118 \\
\swift\ XRT & 2005 May 21 & 1.48 (0.04)~$\times$ 10$^{-2}$ & 1.71 (0.05) & 0.38 (0.10) & 2.4  & 
4.0 $\times$ 10$^{-11}$ & 0.90/196 \\
   &         & 1.46 (0.04)~$\times$ 10$^{-2}$ & 1.78 (0.03) & 0.18 frozen   & 3.5  & 
4.2 $\times$ 10$^{-11}$ & 0.94/197 \\
\swift\ XRT & 2005 May 22 & 1.66 (0.02)~$\times$ 10$^{-2}$ & 1.90 (0.02) & 0.18 (0.04) & 1.9  & 
4.1 $\times$ 10$^{-11}$ & 1.03/408 \\
\swift\ XRT & 2005 May 29 & 1.31 (0.04)~$\times$ 10$^{-2}$ & 1.77 (0.06) & 0.34 (0.11) & 2.2  & 
3.3 $\times$ 10$^{-11}$ & 1.01/181 \\
    &        & 1.29 (0.04)~$\times$ 10$^{-2}$ & 1.83 (0.04) & 0.18 frozen   & 2.7  & 
3.5 $\times$ 10$^{-11}$ & 1.03/182 \\
\swift\ XRT & 2005 June 24 & 1.52 (0.05)~$\times$ 10$^{-2}$ & 1.79 (0.06) & 0.26 (0.11) & 2.5  & 
4.1 $\times$ 10$^{-11}$ & 1.09/183 \\
\hline
 & & & & & & & \\[-8pt]
{\it Beppo}SAX LECS+MECS & 1999 Feb. 20 & 0.77 (0.07)~$\times$ 10$^{-2}$ & 1.57 (0.10) & 0.48 (0.10) 
& 2.8  & 2.3 $\times$ 10$^{-11}$ & 1.23/55  \\
{\it Beppo}SAX LECS+MECS & 1999 April 07 & 0.69 (0.06)~$\times$ 10$^{-2}$ & 1.82 (0.10) & 0.42 (0.10) 
& 1.6  & 1.5 $\times$ 10$^{-11}$ &  0.91/55 \\
\hline
\end{tabular}}
\medskip
$^{(1)}$ Numbers in parenthesis are statistical errors at the 90\% confidence level. 
$^{(2)}$~Fluxes in the 2--10~keV energy band are corrected for Galactic absorption.
\end{table}