\begin{table}%t5
\caption{\label{orl_ab}Ionic abundances from ORLs.}
%\centerline
{
\begin{tabular}{lllcc}
\hline
\hline
Ion &$\lambda$~(\AA)  & Mult &  $I$      & $N_{{\rm X}^{i+}}/N_{{\rm H}^+}$\\
\hline
He$^+$  & 4471.50    & V14  & 5.990        & 1.14($-$1) \\
        & 5875.66    & V11  & 18.06        & 1.19($-$1) \\
        & 6678.16    & V46  & 4.234        & 1.05($-$1) \\
        & Average    &      &              & 1.15($-$1) \\
He$^{2+}$& 4685.68   &  3.4 & 4.359        & 3.63($-$3) \\
\noalign{\vskip8pt}
C$^{2+}$& 4267.15    & V6  & 0.531          & 5.18($-$4)\\
\noalign{\vskip8pt}
N$^{2+}$ &4041.31     & V39b  & 0.138        & 9.37($-$4)\\
        &4043.5290   & V39a  & 0.087        &7.69($-$4)\\
        &Average     &       &              & 8.53($-$4)\\
N$^{3+}$&4379.11  & V18    & 0.710 & 3.03($-$4)\\
\noalign{\vskip8pt}
O$^{2+}$& 4649.13$^{{a}}$    & V1   & 0.420          & 8.37($-$4) \\
    & 4676.24$^{{a}}$    & V1   & 0.137          & 1.22($-$3) \\
    &4349.43    & V2   & 0.305          & 1.62($-$3) \\
    &4072.16  & V10  & 0.213          & 8.93($-$4) \\    
    &4156.53$^{{b}}$ & V19  & 0.126          & 1.02($-$2) \\
    &Average    &         &               & 1.14($-$3)\\
\hline
\end{tabular}}
\smallskip
$^{{a}}$ Possibly affected by absorption features from the cool 
    stellar component (cf. Sect.~5).\\
  $^{{b}}$  Possibly contaminated by other lines. Discarded
    when calculating the average ionic abundance.
\end{table}