\begin{table}%t1
\caption{\label{table1}The average continuum flux and slope of the Baldwin effect
in four different observation epochs.  The standard deviations of
these two values are also given. The flux is in units of $\rm
10^{-13}~erg~s^{-1}~cm^{-2}~\AA^{-1}$.  } 
$$
\begin{array}{cccccccc}
\hline \hline\noalign{\smallskip} \rm{Epoch} & \rm{JD~~time} &
\rm{No.~of~spectra} &F_{1440~\rm \AA} & \sigma(F_{1440~\rm \AA}) &
\alpha & \beta & \sigma
\\
\noalign{\smallskip}
\hline
1& \rm{JD~2~443~722{-}JD~2~445~654} & \rm{75(IUE)} & 1.077 & 0.574 & 0.721 & -0.279 & 0.025\\
2& \rm{JD~2~445~766{-}JD~2~447~631} & \rm{85(IUE)} & 0.490 & 0.307 & 0.833 & -0.167 & 0.059\\
3& \rm{JD~2~447~948{-}JD~2~450~243} & \rm{308(IUE)+7(HUT)}& 3.607 & 1.294 & 0.581 & -0.419 & 0.025\\
4 & \rm{JD~2~450~855{-}JD~2~452~403} & \rm{15(HST)}& 0.844 & 0.754 & 0.777 & -0.223 & 0.056\\
\hline
\end{array}
$$
\end{table}