\begin{table}%t2
\caption{\label{tab:sensibility}Flux density upper limits for the four sources at the analysed frequencies.}
%%\centering

\par
\begin{tabular}{lcc}
\hline \hline \noalign{\smallskip}
\multirow{2}{*}{Source} &\multicolumn{2}{c}{$S_{\rm max}$ ($\mu$Jy)}\\
&6.5 GHz& 8.5 GHz\\
\hline
\otto&52&25\\
\sette&--&31--30\\
\nove&68&26\\
\hline
&5 GHz& 6 GHz\\
\sax &59&59\\
\hline
\end{tabular}
\tablefoot {For \sette\ the two observations are both at~8.5~GHz.}
\end{table}