\begin{table}%t1
%\centering
\par
\caption{\label{tab:blocks}Overview of the \inte data of Vela X-1.}
\begin{tabular}{llll}
\hline\hline
\noalign{\smallskip}
& Revolutions & MJD & Exposure \\
\hline
 Block 1  & 137$-$141  & 52~970.4$-$52984.9 & 0.92~Ms \\
 Block 2  & 373$-$383  & 53~678.7$-$53708.2  & 1.57~Ms \\
 Block 3  & 433$-$440  & 53~857.1$-$53879.0 & 1.13~Ms \\
\hline
\end{tabular} \vspace*{-0.5mm}
\end{table}