\begin{table}%t5
\caption{\label{tt8}Variability parameters.}
\small%%\centering

\par
\begin{tabular}{lccccc}
\hline \hline\noalign{\smallskip}
 Feature      &       Region (obs) [\AA] &  $F$(mean)\tablefootmark{a} & $\sigma$($F$)\tablefootmark{a} & $R$(max)/$R$(min) & $F$(var) \\
 \hline
 continuum           &      5369--5399 &   2.31   & 1.07    &   5.2     &     0.46 \\
 H$\beta$ -all      &      4909--5353 &   2.39   & 0.91    &   4.7     &     0.38 \\
 H$\alpha$-all       &      6740--7160 &   9.42   & 3.36    &   3.4     &     0.35 \\
 \noalign{\smallskip}
 H$\beta$-blue wing &      4977--5097 &   0.88   & 0.37    &   4.9     &     0.41 \\
 H$\beta$-core      &      5097--5165 &   0.63   & 0.24    &   4.7     &     0.38 \\
 H$\beta$-red wing  &      5165--5268 &   0.70   & 0.26    &   4.3     &     0.37 \\
 \noalign{\smallskip}
 H$\alpha$-blue wing &      6720--6882 &   4.13   & 1.70    &   3.5     &     0.40 \\
 H$\alpha$-core      &      6882--6974 &   2.63   & 1.16    &   4.3     &     0.42 \\
 H$\alpha$-red wing  &      6974--7136 &   2.97   & 1.07    &   3.4     &     0.35 \\
 \noalign{\smallskip}
 H$\beta$-blue part &      4977--5131 &   1.20   & 0.48    &   4.8     &     0.39 \\
 H$\beta$-red  part &      5131--5268 &   1.00   & 0.38    &   4.5     &     0.38 \\
 \noalign{\smallskip}
 H$\alpha$-blue part &      6720--6928 &   5.46   & 2.23    &   3.6     &     0.40 \\
 H$\alpha$-red part  &      6928--7136 &   4.24   & 1.66    &   3.7     &     0.38 \\
\hline  
\end{tabular}
\tablefoot{Column~(1): the mean flux. Column~(2): the flux standard
deviation. Column~(3): the ratio of the maximum to the minimum flux in
the monitoring period. Column~(4): the measured (uncertainty-corrected)
estimate of the variation amplitude with respect to the mean flux.\\
\tablefoottext{a}{The continuum flux is in units $10^{-15}~\rm erg~cm^{-2}~s^{-1}~A^{-1}$, and the line flux is in $10^{-13}~\rm erg~cm^{-2}~s^{-1}$.}} 
\end{table}