\begin{table}%t2
 \caption{\label{slab_vel}Flow and rms (broadening) velocities of the ions with the strongest absorption lines in the Obs.~2 RGS~spectrum, determined from the {\it slab} model best fit.}
%\small
%\centering
\par
\begin{tabular}{l l l l}
\hline \hline\noalign{\smallskip}
{Ion} & Flow $v$\tablefootmark{a}   & Rms $v$\tablefootmark{a} & Observed transitions \\ 
\hline
\ion{C}{vi}~& $-800 \pm 100$ & $300 \pm 100$ & Ly-$\alpha$, Ly-$\beta$, Ly-$\gamma$\\
\ion{N}{vi}~& $-700 \pm 300$ & $600 \pm 200$ & He-$\alpha$, He-$\beta$, He-$\gamma$\\
\ion{N}{vii}~& $-800 \pm 300$ & $900 \pm 300$ & Ly-$\alpha$, Ly-$\beta$, Ly-$\gamma$\\
\ion{O}{vii}~& $-900 \pm 100$ & $300 \pm 100$ & He-$\alpha$, He-$\beta$, He-$\gamma$, He-$\delta$\\
\ion{O}{viii}~& $-1000 \pm 100$ & $370 \pm 40$ & Ly-$\alpha$, Ly-$\beta$, Ly-$\gamma$, Ly-$\delta$\\
\hline
\end{tabular}
\tablefoot {\tablefoottext{a}{km ${\rm s}^{-1}$.}}
\end{table}