\begin{table}%t3
%\centering
\par
\caption{Summary of detected periodicities.\label{periods}}
$$
\begin{array}{lcrcr}
\hline\hline
\noalign{\smallskip}
{\rm Description} & {\rm Flag} & N & {\rm Flag} & N\\
 & \multicolumn{2}{c}{{\rm RED}} & \multicolumn{2}{c}{{\rm BLUE}} \\
 \hline
{\rm No~curve}       & 0 &   8 & 0 &   9 \\
{\rm Good}            & 1 &  96 & 2 &  91 \\
{\rm Poor}            & 5 & 103 & 5 & 208 \\
{\rm Multi-Periodic}  & 6 &  91 & 6 &  91 \\
{\rm Alias}           & 9 & 160 & 9 &  59 \\
\noalign{\smallskip}
\hline
\end{array}
$$
\end{table}