\begin{table}%t1
  \caption{\label{tab:sample}Sample summary.}
%\centerline
 {    \begin{tabular}{lcccc}
    \hline
    \hline
    \noalign{\smallskip}
    Band (keV) &  $N_{\rm obs}$$^a$ & $N_{\rm sou}$$^b$ & Flux limit   & Area       \\
               &                &               &  (\cgs{})    & (deg$^{2}$) \\
    \noalign{\smallskip}
    \hline
    \noalign{\smallskip}
    Soft (0.5--2)       &  1063 & 31~288 & $1.4\times10$$^{-15}$  & 125.52  \\
    Hard (2--10)        &  1063 & 9188  & $9.2\times10$$^{-15}$  & 125.52   \\
    Ultrahard (4.5--10)$^c$ &  432  & 1259  & $1.4\times10$$^{-14}$  & 51.47   \\
    \noalign{\smallskip}
    \hline
\end{tabular}}
\par
\smallskip
    {$^a$ Number of \XMM{} observations used.} 
    {$^b$ Number X-ray sources used.} 
    {$^c$ For observations with exposure times $>$20~ks only.} 
\end{table}