\begin{table}%t5 \caption{\label{table:7}Parameters for the best-fit model to the observed $^{12}$CO and $^{13}$CO line profiles.} %\centering \par \begin{tabular}{c l c c c c c c c c} \hline\hline \noalign{\smallskip} & $R_{{\rm i}}$ & $R_{{\rm out}}$ & Mass-loss late & $f_{{\rm CO}}$ & $V_{{\rm exp}}$ & $T_{0}$ & $\alpha$ & $T_{{\rm bg}}$ \\ & (10$^{14}$ cm) & (10$^{14}$ cm) & ($M_{\odot}$ yr$^{-1}$) & (10$^{-4}$) & (km~s$^{-1}$) & (K) & & (K) \\ \hline $^{{\rm 12}}$CO & 1 & 630 & 4.7 $\times$ 10$^{-6}$ & 3 & 18 & 40 & 0.8 & 2.7 \\ $^{{\rm 13}}$CO & 1 & 700 & 4.7 $\times$ 10$^{-6}$ & 0.35 & 18 & 50 & 0.8 & 2.7 \\ \hline \end{tabular} \tablefoot{$R_{\rm i}$ represents the inner radius of the envelope, $R_{{\rm out}}$ the outer radius and $f_{{\rm CO}}$ = [CO/H$_2$] the CO abundance relative to H$_2$. The last three columns give the values for the parameters in Eq.~(\ref{eqTemp}). The expansion velocity is derived from the $^{12}$CO(3--2) observations.} \end{table}