\begin{table}%t2
%\centering
\par
\caption{\label{table1}Observed and  theoretical ($\ell=1$)  periods of the best-fit 
         model for PG~2131+066 ($M_*= 0.589~M_{\odot}$, $T_{\rm eff}=
         102~179$~K,  $\log(L_*/L_{\odot})=  1.57$). Periods  are  in
         seconds and rates of period change (theoretical) are in units
         of  $10^{-12}$~s/s.  The  observed  periods  are taken  from
         Kawaler et~al. (\cite{Kawaler95}).}
\begin{tabular}{ccccc}
\hline
\hline\\[-3.2mm]
$\Pi_i^{\rm O}$ & $\Pi_k^{\rm T}$ & $k$ & $\dot{\Pi}^{\rm T}_k$ & 
Unstable\\[-3.2mm]\\
\hline
$ 341.45 $ & $341.88  $ & 14 & $2.04 $ &  yes     \\
---        & $363.66  $ & 15 & $3.90 $ &  yes     \\   
$ 384.27 $ & $383.94  $ & 16 & $2.60 $ &  yes     \\
$ 403.93 $ & $403.30  $ & 17 & $3.30 $ &  yes     \\
$ 426.36 $ & $426.48  $ & 18 & $4.14 $ &  yes     \\
$ 450.28 $ & $445.31  $ & 19 & $2.89 $ &  yes     \\
$ 462.39 $ & $465.91  $ & 20 & $4.53 $ &  yes     \\
---        & $488.81  $ & 21 & $4.11 $ &  no      \\   
$ 507.91 $ & $507.91  $ & 22 & $3.79 $ &  no      \\
\hline
\end{tabular}
\end{table}