\begin{table}%t2
\caption{\label{tab2}Phases $\phi$ for the the central minima and the lengths of the bright intervals, with $\phi=0$ referring to the optical
  minimum. }
\small %\centerline
 {\begin{tabular}{l@{\hspace{10mm}}c@{\hspace{8mm}}c@{\hspace{6mm}}c@{\hspace{6mm}}l} 
\hline \hline \noalign{\smallskip}
Observation & $\phi_{\rm min/dip}$ & \multicolumn{3}{c}{Bright phase interval~$^{(1)}$} \\
 &  &  $\phi_{\rm start}$ &  $\phi_{\rm end}$ &  $\phi_{\rm center}$\\
 \hline
Optical 1987 & $0.000$ & $-0.34$ & $0.32$ & $-0.01$ \\ 
{\it ROSAT} 1992/1993 & $0.026$ & $-0.34$ & $0.26$ & $-0.04$\\ 
{\it EUVE} 1994/1999  & $0.026$ & $-0.33$ & $0.27$ & $-0.03$\\ 
{\it MONET/N} 2009 & $0.000$ & $-0.33$ & $0.31$ & $-0.01$\\ 
\hline 
\end{tabular}}
\medskip
$^{(1)}$ Errors typically 0.01, except for the 1987 data, where they are 0.02.
\end{table}