\begin{table}%t2
\caption{\label{tab:rgs_lines}Spectral lines identified in the first order {\em XMM-Newton} RGS~spectrum of~TW~Hya. {\em left} -- Observed line center, width, number of counts, and photon flux. Uncertainties include statistical 1$\sigma$~error plus a systematic error stemming from the uncertainty of the local background level (see text for details). {\em right} --  Line identifications from \protect\citey{Mewe85.1}, \protect\citey{Mewe95.1}, and \protect\citey{Phillips99.1}. For line blends we list the most likely contributors according to X-ray observations of other stars.
}
 %\centering
\par
\begin{tabular}{rrrr|llr} \hline\hline
\multicolumn{1}{c}{$\lambda$} & \multicolumn{1}{c}{$\sigma$} & \multicolumn{1}{c}{$I$} & \multicolumn{1}{c|}{Photon Flux} & \multicolumn{3}{c}{Identification} \\
\multicolumn{1}{c}{[\AA]} & \multicolumn{1}{c}{[\AA]} & \multicolumn{1}{c}{[cts]} & \multicolumn{1}{c|}{[$10^{-5}~\frac{\rm ph}{\rm s~cm^2}$]} & Ion & Trans. & $\lambda$ \\
\hline
\multicolumn{7}{c}{\bf RGS~1} \\
\hline
$18.983$ & $0.055$  & $465.7 \pm 43.7$ & $30.4 \pm 2.8$ & O~VIII & $Ly_\alpha$ & 18.97 \\
$21.616$ & $0.047$  & $241.6 \pm 28.4$ & $17.4 \pm 2.1$ & O~VII & $r$ & 21.61 \\
$21.836$ & $0.053$  & $128.2 \pm 20.1$ & $ 9.5 \pm 1.5$ & O~VII & $i$ & 21.80 \\
$22.100$ & $0.037$  & $  5.3 \pm  7.1$ & $ 0.4 \pm 0.6$ & O~VII & $f$ & 22.10 \\
\hline
\multicolumn{7}{c}{\bf RGS~2} \\
\hline
$12.152$ & $0.060$ & $111.4 \pm 26.1$ & $ 6.3 \pm 1.5$ & Ne~X    & $Ly_\alpha$ & 12.13 \\
$13.460$ & $0.050$ & $402.0 \pm 38.1$ & $23.1 \pm 2.2$ & Ne~IX & $r$ & 13.45 \\
$13.560$ & $0.057$ & $308.9 \pm 19.9$ & $17.4 \pm 1.1$ & Ne~IX & $i$ & 13.55 \\
$13.710$ & $0.054$ & $149.7 \pm 27.3$ & $ 8.2 \pm 1.5$ & Ne~IX & $f$ & 13.70 \\
$17.065$ & $0.075$ & $ 46.8 \pm 15.9$ & $ 2.7 \pm 0.9$ & Fe~XVII & $Ne3G$ & 17.06 \\
$24.793$ & $0.060$ & $171.5 \pm 31.5$ & $11.8 \pm 2.2$ & N~VII  & $Ly_\alpha$ & 24.78 \\
$28.820$ & $0.059$ & $ 32.1 \pm 14.2$ & $ 2.9 \pm 1.3$ & N~VI   & $r$ & 28.79 \\
$29.101$ & $0.030$ & $ 14.2 \pm  7.2$ & $ 1.3 \pm 0.6$ & N~VI   & $i$ & 29.10 \\
$29.540$ & $0.030$ & $  4.3 \pm  5.8$ & $ 0.4 \pm 0.5$ & N~VI   & $f$ & 29.54 \\
\hline
\multicolumn{7}{c}{\bf RGS~1 + RGS~2} \\
\hline
$16.030$ &  $0.056$ & $118.7 \pm 37.2$ & $ 3.5 \pm 1.1$ &  Fe~XVIII & & 16.00 \\
         &         &                  &                 &  O~VIII & $Ly_\beta$ &$16.01$ \\
$18.649$ &  $0.037$ & $ 53.4 \pm 12.1$ & $ 1.7 \pm 0.4$ &  O~VII  & $He3A$ & 18.63 \\
$33.757$ &  $0.065$ & $113.9 \pm 20.7$ & $ 7.8 \pm 1.4$ &  C~VI   & $Ly_\alpha$ & 33.70 \\
\hline
\end{tabular}
\end{table}