\begin{table}%t6
\caption{Short-term frequencies found by successive pre-whitening. We list frequency, period,
and semi-amplitude  as well as the peak height $S$ in the periodograms.
Errors are given in parentheses in units of the last digit.}\label{tab6}
%\centering
\par
\begin{tabular}{ccccc}
\hline  \hline
     & $f$ [\cd ]& $P$ [d]& $K$ [\ms ] & $S$\\
     \hline
$f_1$& 56.600(4)& 0.017668(1)& 151(27) & 0.077\\
$f_2$& 64.189(6)& 0.015579(1)&  99(26) & 0.041 \\
\hline
\end{tabular}
\end{table}