\begin{table}%t3
%\centering
\par
\caption{\label{X-ray:log} X-ray observations of \WRXXIa.}
$$
\begin{tabular}{lllrr@{~$\pm$~}lc}
\hline \hline Date       & Dataset ID               & Instrument      &
Time          & \mC{2}{c}{Count rate} & \Lx  \\
           &                          &                 & (s)         & \mC{2}{c}{($\persec$)}  &(\Lu) \\
\hline  %
1979-07-13 & \ads{einstein}{3341}     & Einstein-IPC    &  1324 & 0.036  & 0.002                   &  0.60~$\pm$~0.03  \\
%\hline
1980-07-08 & \ads{einstein}{7715}     & Einstein-IPC    &  7680
& 0.0592 & 0.0002                  &  0.99~$\pm$~0.01  \\
%\hline
1980-07-10 & \ads{einstein}{7716}     & Einstein-HRI    &  7006
& 0.006  & 0.002                   &  0.82~$\pm$~0.27  \\
%\hline
1990-10-01 & \ads{rosat}{RS932717N00} & RASS            &   180
& 0.0778 & 0.0233                  &  1.03~$\pm$~0.31  \\
%\hline
1992-07-29 & \ads{rosat}{RP400329N00} & ROSAT-PSPC      &  8396
& 0.0817 & 0.0031                  &  1.08~$\pm$~0.04  \\
%\hline
1994-01-14 & \ads{rosat}{RH201611N00} & ROSAT-HRI       &   696
& 0.0177 & 0.0059                  &  0.67~$\pm$~0.22  \\
%\hline
1994-07-31 & \ads{rosat}{RH201611A01} & ROSAT-HRI       & 17~906
& 0.0108 & 0.0012                  &  0.41~$\pm$~0.04  \\
%\hline
1997-11-29 & \ads{rxte}{301120101}    & RXTE-PCA        & 12~000
& 7.088  & 0.079                   &  4.94~$\pm$~0.06  \\
%\hline
1998-01-21 & \ads{asca}{26014000}     & ASCA-GIS2       & 36~858
& 0.0518 & 0.0012                  &  1.76~$\pm$~0.04  \\
%\hline
1998-12-27 & \ads{asca}{46009000}     & ASCA-GIS2       & 21~174
& 0.0817 & 0.0020                  &  1.44~$\pm$~0.04  \\
           &                          & ASCA-SIS0       & 21~788     & 0.1208 & 0.0024                  &                 \\
\hline 
\end{tabular}
$$
\end{table}