\begin{table}%t2
%\centering
\par
\caption{Summary of the twelve Galactic center observation campaigns of 
  the WFCs. Shown are the time frames of the campaigns,  the number of 
  observations, the net exposure time and the number of 
  bursts seen from \bron.\label{tab2}}
\begin{tabular}{ccrrr}
\hline \hline
\multicolumn{2}{c}{Campaign} & 
\multicolumn{1}{r}{\# obs.} & 
\multicolumn{1}{r}{$t_{\mathrm{exp}}~(\rm{ks})$} & 
\multicolumn{1}{r}{\# bursts} \\
\hline
1996 & Aug. 15--Oct. 29 & 67 & 1017 &  0  \\
1997 & Mar. 02--Apr. 26 & 21 &  654 &  0  \\
1997 & Sep. 06--Oct. 12 & 13 &  302 &  0  \\
1998 & Feb. 11--Apr. 11 & 17 &  551 & 14  \\
1998 & Aug. 22--Oct. 23 & 10 &  410 &  0  \\
1999 & Feb. 14--Apr. 11 & 14 &  470 &  3  \\
1999 & Aug. 24--Oct. 17 & 24 &  801 &  0  \\
2000 & Feb. 18--Apr. 07 & 21 &  633 &  8  \\
2000 & Aug. 22--Oct. 16 & 29 &  767 &  8  \\
2001 & Feb. 14--Apr. 23 &  5 &  215 &  0  \\
2001 & Sep. 04--Sep. 30 &  7 &  284 &  9  \\
2002 & Mar. 05--Apr. 15 &  5 &   91 &  0  \\
\hline
\end{tabular}
\end{table}