\begin{table}%t2
%\centering
\par
\caption{\label{tab-model}Parameters used in the modelling of the line emission.}
\small\begin{tabular}{ l l}
\hline \hline 
Distance                         & 150 pc \\
Stellar effective temperature ($T_{\rm eff}$) & 2600 K \\
Stellar luminosity ($L_{*}$)     & $7.5\times 10^{3}$ $L_{\odot}$ \\
Gas terminal velocity ($v_{\rm exp}$)     & 8.5 km s$^{-1}$ \\
Inner radius of the shell ($R_{\rm in}$) & $2\times 10^{14}$ cm\\
Gas mass-loss rate  ($\dot{M}$)    & $7\times 10^{-7}$ $M_{\odot}$ yr$^{-1}$ \\
CO abundance (CO/H$_{2}$)          & $6\times 10^{-4}$  \\
ortho-H$_{2}$O abundance (o-H$_{2}$O/H$_{2}$)  &  $7.5\times 10^{-6}$ \\
para-H$_{2}$O abundance (p-H$_{2}$O/H$_{2}$)  &  $3.6\times 10^{-6}$ \\
\hline
\end{tabular}%\vspace*{-2mm}
\end{table}