\begin{table}%t13
 %\centering
\par
       \caption{Comparison between the radius of the layer reported in this paper and the average radius of the SiO maser ring of \cite{cotton2004} for R~Leo, \object{Mira} and U~Ori.\label{tab:sio}}
       \begin{tabular}{cccc}            \hline             \hline            \noalign{\smallskip}Star  &~$R_{{\rm layer}}$ &~$R_{{\rm SiO}}$ &~$R_{{\rm SiO}}/R_{{\rm layer}}$ \\
         &       (mas)   &    (mas)    &        \\           \noalign{\smallskip}            \hline            \noalign{\smallskip}
\object{R Leo} & 25.00 & 30.6 & 1.22\\
\object{Mira} & 24.95 & 37.8 & 1.52\\
\object{U Ori} & 12.00 & 14.4 & 1.20\\    \noalign{\smallskip}            \hline         \end{tabular} 
\end{table}