\begin{table}%t1
\par
 \caption {\label{tab:obs}\textit{XMM-Newton} observations used in this paper.}
 %\centerline
 { \begin{tabular}{llccc}
 \hline
 \hline
   &                  &     \multicolumn{3}{c}{Exposure (ks) }   \\ 
   &                 &      \multicolumn{2}{c}{MOS }  & PN \\
 ObsId & Observation date &  Total & Good  & Good \\
 \hline
   0093670101 (NE) &  2001 September 5 & 15.3 & 1.8 & 0\\
   0093670201 (NW) &  2001 September 5 & 15.3 & 6.7  & 0\\
   0093670301 (SW) &  2001 September 8 & 15.3 & 15.2  & 10.0\\
   0093670401 (SE) &  2002 March 14 & 14.1 & 11.6  & 5.1\\
   0093670501 (CE) &  2001 March 2  & 13.8 & 13.0  & 6.5\\
   0207300201 (CE) &  2004 February 22 & 31.5 & 12.4  & 0.\\
   0203470401 (NE) &  2004 March 25 & 17.0 & 16.1   & 6.7\\
   0203470501 (NW) &  2004 March 25  & 18.0 & 13.1  & 9.7\\
   0502080101 (E) &  2007 September 15 & 34.6 & 5.8  & 0\\ 
   0502080301 (W) &  2007 October 3 & 8.9 & 2.8  & 0\\
   0551030101 (S) &  2008 September 27 & 24.9 & 24.5 & 20.8\\
 \hline
 \end{tabular}}
 \smallskip
  The total and good columns represent
 the exposure time before and after flare screening.
 \end{table}