\begin{table}%t4
\caption{\label{tab:linerat}Line ratios sensitive to optical depth.}
\small%\centerline
 {
\begin{tabular}{lrccc}
\hline\hline
&&&& \\[-8pt]
Star & $N_{\rm H}~({\rm cm^{-2}})$ & $\frac{\ion{O}{vii}(r)}{\ion{O}{vii}(18.6)}$ & $\frac{\ion{O}{viii}(Ly\alpha)}{\ion{O}{viii}(Ly\beta)}$ & $\frac{\ion{Fe}{xvii}(15.0)}{\ion{Fe}{xvii}(16.8)}$  \\[2pt]
\hline
&&&& \\[-8pt]
\object{MP~Mus}       & $5\times10^{20}$   & $4.0\pm1.5$   & $3.2\pm1.0$   & $1.3\pm0.4$   \\
\object{TW~Hya}       & $2\times10^{20}$   & $9.4\pm2.8$   & $7.0\pm2.6$   & $1.9\pm1.1$   \\
\object{TWA~5}        & $3\times10^{20}$   & $8\pm4$       & $11\pm4$      & $1.4\pm0.4$   \\
\hline
&&&& \\[-8pt]
\object{Procyon}      & $1.1\times10^{18}$ & $7.9\pm1.1$   & $\cdots$      & $1.2\pm0.4$   \\
\object{AT~Mic}       & $1\times10^{18}$   & $6.2\pm2.6$   & $\cdots$      & $1.8\pm0.6$   \\
\object{$\delta$~CrB} & $\cdots$           & $\cdots$      & $\cdots$      & $2.4\pm0.4$   \\
\object{YZ~CMi}       & $1.2\times10^{18}$ & $\cdots$      & $\cdots$      & $1.2\pm0.4$   \\
\object{44~Boo}       & $1\times10^{18}$   & $\cdots$      & $\cdots$      & $2.39\pm0.28$ \\
\object{$\alpha$~Cen} & $\cdots$           & $9.7\pm1.0$   & $\cdots$      & $\cdots$      \\
\object{Capella}      & $1.8\times10^{18}$ & $\cdots$      & $\cdots$      & $1.64\pm0.12$ \\
\object{AB Dor}       & $1.7\times10^{19}$ & $8.9\pm1.6$   & $\cdots$      & $1.85\pm0.10$ \\
\hline
\end{tabular}}
\medskip
Ratios are derived from line fluxes in ${\rm ph~s^{-1}~cm^{-2}}$. Active stellar measurements are taken from: \citet{RaassenMewe2002} for Procyon; \citet{RaassenMewe2003} for AT~Mic; \citet{Gondoin2005} for $\delta$~CrB; \citet{RaassenMitra-Kraev2007} for YZ~CMi; \citet{Gondoin2004} for 44~Boo; \citet{AudardBehar2001} for Capella; \citet{SanzForcadaMaggio2003} for AB~Dor.
\end{table}