\begin{table}
\caption{\label{table:1}Observations used in this paper.}          
%%\centering
\par
\par
\begin{tabular}{l c c c c}       
\hline\hline\noalign{\smallskip}              
ID & Date & Length & RGS & PN\\    
   &      &  (ks)  &  (ks)   &  (ks)  \\
\hline                        
   0150390101 & 2003 April 6 & 108 & 67.8 & 63.8 \\     
   0150390301 & 2003 April 8 & 92  & 77.8 & 67.8 \\
\hline                                  
\end{tabular}
\tablefoot{We report the total exposure length together with the net exposure time remaining after screening of the background and removal of bursts.}
\end{table}