\begin{table}%t3
  %\centering
\par
  \caption{Criteria adopted to separate the secondaries with multi-color observations into confirmed companions, candidate companions, and background stars. The $\chi^2$ values of 2.30 and 11.8 correspond to the $1\sigma$ and $3\sigma$ levels. This means that (statistically) 68.3\% of the physical companions have $\chi^2 < 2.30$ and 99.73\% of the physical companions have $\chi^2 < 11.8$. A secondary with $\chi^2 < 2.30$ is very likely a companion star. A secondary with $\chi^2 > 11.8$ is almost certainly a background star. The secondaries with $2.30 < \chi^2 < 11.8$ may be companions or background stars.  \label{table: classification}}
  \begin{tabular}{lcp{0.6cm}p{0.1cm}p{0.9cm}}
    \hline\hline
    Secondary status    & Symbol   & \multicolumn{3}{l}{Criterion}\\
    \hline
    Confirmed companion &c &         &$ \chi^2$&$\leq 2.30$ \\
    Candidate companion &? & $2.30<$ &$\chi^2$&$\leq 11.8$ \\
    Background star     &b & $11.8<$ &$\chi^2$&  \\
    \hline
  \end{tabular}  
\end{table}