\begin{table}%t8
%\centering
\par
 {\footnotesize %\centering
\par
 \caption {\label{tab:sample_means}Mean values of the X-ray luminosity classes (see Tables~\ref{tab:EMSS_LX_class} 
 and~\ref{tab:sample_L_X}, respectively).}
\begin{tabular}{c  c c }
\hline\hline
\noalign{\smallskip}
$L_{\rm X}$ & EMSS sample & RBS sample\\
class & $\times10^{45}$~erg/s & $\times10^{45}$~erg/s\\
\hline
 \tt I \rm   & $\langle L_{\rm X}\rangle=0.16$  & $\langle L_{\rm X}\rangle=0.24$ \\
 \tt II \rm  & $\langle L_{\rm X\rangle}=0.26$  & $\langle L_{\rm X}\rangle=0.50$ \\
 \tt III \rm & $\langle L_{\rm X}\rangle=0.49$  & $\langle L_{\rm X}\rangle=1.62$ \\
\hline
\end{tabular} }
\vspace*{-3mm}\end{table}