\begin{table}%t1
\caption{\label{tab11}Main characteristics of the X-ray observations presented here.} 
%\centering
\par
\begin{tabular}{l c c l c c}      
\hline \hline \noalign{\smallskip}
Instr.\tablefootmark{\star}&Exp.\tablefootmark{\dagger}&CR\tablefootmark{\ddagger} & Instr.\tablefootmark{\star}&Exp.\tablefootmark{\dagger}&CR\tablefootmark{\ddagger}\\
&ks&c/s&&ks&c/s\\
\hline       
Epn&38&1.10\tablefootmark{a}& RGS1&63& 0.08\tablefootmark{b}\\
EMOS1&49&0.37\tablefootmark{a} &RGS2&63& 0.08\tablefootmark{b}\\
EMOS2&50&0.37\tablefootmark{a}&ACIS-S&60&0.32\tablefootmark{a}\\
\hline
\end{tabular}
\tablefoot {\tablefoottext{\star}{Detector name;} 
\tablefoottext{\dagger}{net exposure;} 
\tablefoottext{\ddagger}{measured count-rate;} 
\tablefoottext{a}{count-rate in the 0.2$-$10~keV band;} 
\tablefoottext{b}{count-rate in the 0.4$-$1.2~keV.}}
\end{table}