\begin{table}%t1
\caption{\label{obs}Observational parameters.}
\small%\centering
\par
\begin{tabular}{rcccc}
\hline\hline
\multicolumn{1}{c}{Transition} &\multicolumn{1}{c}{Frequency}&\multicolumn{1}{c}{{\it HPBW}}&\multicolumn{1}{c}{PA}
&\multicolumn{1}{c}{$\Delta v$}\\
& \multicolumn{1}{c}{(GHz)}&
\multicolumn{1}{c}{($\arcsec$)}&\multicolumn{1}{c}{($^\circ$)}&
\multicolumn{1}{c}{(${\rm km~s}^{-1}$)}\\
\hline\noalign{\smallskip}
$^{13}$CO(2$-$1)&220.3987&5.43~$\times$~1.88&30&0.50\\
CO(2$-$1)&230.5380&5.45~$\times$~2.08&28&0.50\\
CO(6--5)&691.4731&8.9&--&0.05\\
\hline
\end{tabular}
\end{table}