\begin{table}%t2
\caption{\label{tab1}  List of emission lines detected in the RGS spectrum of NGC~5252.}
%\centering
\par
\begin{tabular}{l c c c c}     % 5 columns 
\hline\hline \noalign{\smallskip}      
Identification & $E_c$\tablefootmark{a} & $L$\tablefootmark{b} & $\Delta v$\tablefootmark{c} & $v_{\rm sys}$\tablefootmark{d} \\
& (eV) & (10$^{40}$~erg~s$^{-1}$) &  & \\
\hline  \noalign{\smallskip}                      
C{\sc vi} Ly-${\alpha}$ & $367 \pm 5$ & $3 \pm^{11}_{2}$ & $800 \pm 400$ & 70 \\\noalign{\smallskip}    
O{\sc vii} He-${\alpha}$ (f) & $560.4 \pm 0.2$ & $2.0 \pm^{0.8}_{0.9}$ & $-370 \pm 110$ & 110 \\\noalign{\smallskip}    
O{\sc vii} He-${\alpha}$ (i) & $E_{\rm c} (f) + 7.7$ & $<$0.9 & & \\\noalign{\smallskip}    
O{\sc vii} He-${\alpha}$ (r) & $E_{\rm c} (f) + 13.0$ & $<$1.4 & & \\\noalign{\smallskip}    
O{\sc viii} Ly-${\alpha}$ & $654.0 \pm^{0.7}_{1.2}$ & $0.6 \pm 0.4$ & $300 \pm^{300}_{600}$ & 130 \\[1mm]
\hline                  
\end{tabular}
\tablefoot{
\tablefoottext{a}{Measured line energy;} \tablefoottext{b}{intrinsic line luminosity;}
\tablefoottext{c}{difference between the measured line energy and the laboratory energy expressed in km s$^{-1}$. Only statistical errors on this measurements are quoted;} \tablefoottext{d}{systematic error on $\Delta v$ expressed in km s$^{-1}$ due to residual uncertainties in the RGS aspect solution ($\simeq$8~m\AA)}.}
\end{table}