\begin{table}%t1
   %\centering
\par
  \caption{Coronal magnetic helicity and its variation. The values 
   have been computed using MDI magnetograms at the times shown. 
   This lapse of time includes the three X-ray bursts observed by 
   SXT (see Sect.~\ref{Sect_Evolution_X-ray_events}). 
   The helicity values are in units of 10$^{39}$~Mx$^2$. \label{Table-helicity}}
  \begin{tabular}{cccc}  
  \hline\hline
  $\alpha$ & $H_{\rm cor}$  & $H_{\rm cor}$ & $\Delta |H_{\rm cor}|$ \\
  Mm$^{-1}$& 00:03 UT   & 11:11 UT  & \\
   \hline
  --0.08    & --5.2 & --2.9 & --2.3\\
  --0.11    & --7.5 & --4.2 & --3.3 \\
  \hline
  \end{tabular}
  \end{table}