\begin{table}%t1
\caption{\label{tab:stars}Characteristics of the sample of T~Tauri stars, sorted by H$\alpha$~emission, for which high resolution \mbox{X-ray} spectra have been analyzed. In the case of resolved multiple systems the stellar mass, spectral type, and bolometric luminosity refer to the component responsible for the \mbox{X-ray} emission.}
%\centerline
{
\begin{tabular}{lccrcccc}
\hline
\hline
Name               & Mass          & Spectral & \multicolumn{1}{c}{{\it EW}(H$\alpha$)$^{a}$} & $L_{\rm X}^{b}$   & $\log (L_{\rm X}^{b}/L_{\rm bol})$ & $N_{\rm e}^{c}$   & References$^{d}$ \\
                   & ($M_{\odot}$) & type     & \multicolumn{1}{c}{(\AA)}                   & ${\rm (erg~s^{-1})}$ &                                        & ${\rm (cm^{-3})}$       &            \\
\hline
\object{TW Hya}    & $\sim$$0.7$     & K7       & $-$220.0 \hspace{0.01\textwidth}              & $1.3\times10^{30}$    & $-2.7$                                   & $\sim$$10^{13}$         & 1, 2, 3, 4 \\
\object{TWA 5}     & $\sim$$0.5$     & M1.5     &  $-$13.4 \hspace{0.01\textwidth}              & $6.7\times10^{29}$    & $-3.1$                                   & $<$$10^{11}$            & 2, 5, 6    \\
\object{HD 98800}  & $\sim$$1.1$     & K5       &    0.0 \hspace{0.01\textwidth}              & $4.1\times10^{29}$    & $-3.8$                                   & $\la$$10^{11}$     & 2, 7, 8    \\
\object{PZ Tel}    & $\sim$$1.1$     & K0       &    0.1 \hspace{0.01\textwidth}              & $2.2\times10^{30}$    & $-3.2$                                   & $<$$10^{12}$            & 9, 10, 11   \\
\object{HD 283572} & $\sim$$1.8$     & G5       &    1.1 \hspace{0.01\textwidth}              & $7.8\times10^{30}$    & $-3.1$                                   & $\cdot\cdot\cdot$     & 12, 13, 14 \\
\hline
\end{tabular}}
 \smallskip
$^{a}$~Negative values of H$\alpha$ equivalent width mark an emission line. $^{b}$~\mbox{X-ray} luminosity evaluated in the $6{-}20$~\AA~band, using the {\it XMM}/MOS or {\it Chandra}/HETGS best fit models presented in the relevant papers. $^{c}$~Densities estimated from the \ion{O}{vii} and \ion{Ne}{ix}~triplets. $^{d}$~Data from: (1)~\citet{BatalhaBatalha2002}; (2)~\citet{Reid2003}; (3)~\citet{StelzerSchmitt2004}; (4)~\citet{KastnerHuenemoerder2002}; (5)~this work; (6)~\citet{JensenCohen1998}; (7)~\citet{KastnerHuenemoerder2004}; (8)~\citet{PratoGhez2001}; (9)~\citet{CutispotoPastori2002}; (10)~\citet{ThatcherRobinson1993}; (11)~\citet{ArgiroffiDrake2004}; (12)~\citet{StrassmeierRice1998}; (13)~\citet{FernandezMiranda1998}; (14)~\citet{ScelsiMaggio2005}.
\end{table}