\begin{table}%t1
    %\centering
\par
    \caption{
    Parameters used in our simulations.  All times are expressed in unit of
    $t_{\rm inj}$\label{tab:param} }
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    \begin{tabular}{lccccc}
    \hline\hline
            {data sample} 
            &{$t_{\rm crit}$}
            &
            &$t_{\rm obs}$
            &
            &{$\Delta t_{\rm obs}$}\\
            \cline{3-5}
            &
            &min
            &max
            &est\\
            \hline
    1997 April 7  &0.1095 & 0.68 & 0.92 & 0.8  & 0.946 \\
    1997 April 16 &0.438  & 0    & 0.5  & 0.35 & 4.2   \\
    1999 June     &0.0512 & 1.05 & 1.15 & 1.1  & 4.5   \\
    \hline
    \end{tabular}
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\end{table}