\begin{table}%t4
    \caption{\label{em_xi}Estimates of the ionisation parameter of the warm emitter using the ratio of the fluxes of~\ion{O}{viii}~Ly$\alpha$ and~\ion{O}{vii}~He$\alpha$~emission lines. The fluxes were fitted assuming an~\ion{O}{viii} absorbing column of~10$^{\rm 17.3}$~cm$^{\rm -2}$ and an \ion{O}{vii} column of~10$^{\rm 16.5}$~cm$^{\rm -2}$, both blueshifted by~$-$900~km~s$^{\rm -1}$. The \ion{O}{viii}~Ly$\alpha$ and~\ion{O}{vii}~He$\alpha$~emission lines were assumed to have a blueshift of~$-$400~km~s$^{\rm -1}$ and zero intrinsic width, for fitting purposes.}
              $$
         \begin{array}{p{0.6in}p{0.7in}p{0.43in}}
            \hline\hline
            \noalign{\smallskip}
             Model$^{\rm {a}}$ & A & B \\
             \noalign{\smallskip}\hline\noalign{\smallskip}
             $F_{\rm \ion{O}{vii}}^{\rm {b}}$ & 4 $\pm$ 2 & 3 $\pm$ 1 \\
             $F_{\rm \ion{O}{viii}}^{\rm {b}}$ & 32 $\pm$ 6 & 5 $\pm$ 1 \\
             $X_{\rm ion}^{\rm {c}}$ & 7$^{\rm +8}_{\rm -3}$ & 2$^{\rm +2}_{\rm -1}$ \\
             log $\xi^{\rm {d}}$ & 2.7 $\pm$ 0.2 & 2.2$^{\rm +0.3}_{\rm -0.2}$ \\
            \noalign{\smallskip}
            \hline
         \end{array}
     $$
  \end{table}