\begin{table}%t3
\par
\caption{\label{tab3}{\it Left column}: parameters for the RGS and {\it Chandra}/ACIS thermal model best fits.}
%\centerline
{
\begin{tabular}{lcc} 
\hline \hline
Parameter & RGS & ACIS \\ 
\hline
\multicolumn{3}{l}{Thermal components} \\
$N_{{\rm H},1}$ (10$^{20}$~cm$^{-2}$) & $<$0.4 & $<$1.2\\
$kT_1$ (eV) & $301 \pm 7$ & $400 \pm 130$ \\
$N_1$$^a$ & $6.9 \pm^{1.0}_{0.6}$ & $1.3 \pm^{1.5}_{1.1}$ \\
$N_{{\rm H},2}$ (10$^{20}$~cm$^{-2}$) & $34 \pm^3_2$ & $<$100 \\
$kT_2$ (eV) & $690 \pm^{20}_{30}$ & $650 \pm^{120}_{50}$ \\
$N_2$$^a$ & $8.6 \pm^{0.3}_{0.9}$ & $1.8 \pm^{0.3}_{0.7}$ \\
\hline
\multicolumn{3}{l}{Elemental abundances with respect to solar} \\
$Z_{\rm C}$  & $0.031 \pm^{0.012}_{0.010} $ & $<$1.08\\
$Z_{\rm N}$  & $0.072 \pm^{0.017}_{0.011} $ & $<$0.15\\
$Z_{\rm O}$  & $0.0123 \pm^{0.0022}_{0.0013} $ & $0.031 \pm^{0.030}_{0.015}$ \\
$Z_{{\rm Ne}}$  & $0.030 \pm^{0.003}_{0.004} $ & $0.11 \pm^{0.03}_{0.04}$ \\
$Z_{{\rm Mg}}$  & $0.083 \pm^{0.012}_{0.011} $ & $0.14 \pm 0.03$ \\
$Z_{{\rm Si}}$  & $0.083 \pm^{0.012}_{0.011} $ & $0.15 \pm^{0.05}_{0.06}$ \\
$Z_{{\rm Fe}}$  & $0.023 \pm 0.002 $ & $0.043 \pm ^{0.011}_{0.005}$ \\
\hline
\multicolumn{3}{l}{Blackbody} \\
$kT$ (eV) & $364 \pm 2$ & ... \\
$N$$^b$ & $3.1 \pm^{0.8}_{0.2}$ & ... \\
\hline
\end{tabular}}\medskip
\par
$^a$ In units of $\frac{10^{-17}}{4 \pi [D_{\rm A} (1+z)^2]} \int n_{\rm e} n_{\rm H} {\rm d}V$, where $D_{\rm A}$ is the angular size of the source and $n_{\rm e}$ and $n_{\rm H}$ are the electron and H densities, respectively.
$^b$ In units of 10$^{-4} \frac{L_{39}}{D^2_{10}}$, where $L_{39}$ is the source luminosity in units of 10$^{39}$~erg~s$^{-1}$ and $D_{10}$ is the distance to the source in units of 10~kpc.
\end{table}