\begin{table}%t2
\caption{Spectral fits.\label{tab2}}
\small
%\centerline
{\begin{tabular}{cccc}
\hline\hline
\noalign{\smallskip}
Interval    & $N_{\rm H}$ @ $z$          &Power law     & Mean flux  \\
(s, rest frame)&($10^{21}$ cm$^{-2}$)&$\Gamma$       & (0.5--10 keV) \\
\hline
\noalign{\smallskip}
59--77      &$\rm 2.3^{+2.0}_{-1.2}$&$\rm 1.41^{+0.09}_{-0.09}$&$9.3\times 10^{-9}$\\
77--99      &$\rm 4.0^{+2.0}_{-1.3}$&$\rm 1.84^{+0.11}_{-0.10}$&$6.0\times 10^{-9}$ \\
99--130     &$\rm 2.3^{+1.8}_{-1.1}$&$\rm 1.91^{+0.11}_{-0.10}$&$4.7\times 10^{-9}$\\
130--268    &$\rm 1.9^{+1.5}_{-0.8}$&$\rm 2.34^{+0.10}_{-0.09}$&$8.1\times 10^{-10}$\\
268--89232  &${<}0.9^\#$         &$\rm 1.98^{+0.16}_{-0.20}$&$1.4\times 10^{-12}$\\
\hline
\noalign{\smallskip}
268--506$^*$& ${<}0.7^+$         &$\rm 3.30^{+0.41}_{-0.36}$&$2.3\times 10^{-11}$\\
507--38647  &                &$1.76^{+0.16}_{-0.17}$&$1.9\times 10^{-12}$\\
41152--70835&                &$1.72^{+0.21}_{-0.21}$&$2.1\times 10^{-12}$\\
73793--89232&                &$1.78^{+0.70}_{-0.68}$&$6.6\times 10^{-13}$\\
\hline
\end{tabular}}
\par
\smallskip
$^\#$ The $3\sigma$ ($\Delta\chi=6.43$) upper limit is $2.0\times10^{21}\cmdue$.
$^+$ Value fixed for all the four PC observations. The $3\sigma$ upper limit
is $1.2\times10^{21}\cmdue$.
$^*$~Adding a cut-off to the power law, the photon index is constrained to be 
$3.03^{+0.80}_{-2.11}$ and the high energy cut-off $>$0.5~keV.
\par
\end{table}