\begin{table}%T4
%\centering
\small
\caption{Extensions of stable regions for different models with respect to the
 semimajor axes and the angular distance to the Langange point~$L_4$.}
\begin{tabular}{ccccccc}
\hline\hline
 %& & {} & {} & & &  \\
{}& {M21}& {M22} & {M31} & {M32} &
{M21$^{*}$}&{M31$^{*}$}\\
%{} & & & & & & \\ 
\hline
$a$ (AU)  & 2.68 & 2.68  & 2.93 & 2.93 & {2.68} & {2.93} \\
$e$  & 0.18 & 0.25  & 0.18 & 0.25& {0.18} & {0.18}  \\
$\delta \omega$ & 30$^{\circ}$ &  14$^{\circ}$   &  35$^{\circ}$ &
10$^{\circ}$ & {7$^{\circ}$} & {22$^{\circ}$}  \\ 
$\delta a$ (AU)  & 0.04 & 0.015  & 0.045 & 0.01& {0.012} & {0.032}\\
\hline
\end{tabular}
\par
\label{t4}
\end{table}