\begin{table}%t4
\caption{Spectral lags between channels 1 and~3 measured by
their light curves~($lag13$) and with the CCF~(CCF31).}\label{tab:lag}
%\centering
$$
\begin{tabular}{lcr@{$\;\pm\;$}lr@{$\;\pm\;$}l}
\hline
\hline
 &&
\multicolumn{4}{c}{Spectral lags}
\\
\cline{3-6}
\multicolumn{1}{c}{ Trigger} && \multicolumn{2}{c}{$lag13$ [s]} &
\multicolumn{2}{c}{CCF31 [s] }
  \\
 \hline
907 && 1.3 & 0.3    &1.07 & 0.11\\
973a && 0.75 & 0.08   &0.55 & 0.06\\
973b    && $4\times 10^{-4}$  & 0.06   &0.06   &0.06\\
999 && 0.11 &0.01   &0.06  &  0.06\\
1625    && 0.15 &0.02   &0.13  &0.06\\
1883    && 0.9 &0.1  &0.63  &0.06\\
2083    && 0.23  & 0.03   &0.25 &0.06\\
2156    && 0.27  & 0.05   &0.25  &0.06\\
3257    && 2.2 & 0.8    &1.8 &  0.2\\
3648a    && 2.7  & 0.6    &1.0  &0.3\\
3648b    && 0.4  & 0.1    &0.65 & 0.06\\
3765    && 0.05   & 0.02   &0.06  &0.06\\
3891    &&$ -$0.02   & 0.03   &0.00 &  0.06\\
5478    && 0.8 & 0.3    &0.70  &0.09\\
5563    && 0.07 & 0.01   &0.06  &  0.06\\
6581    && 0.053   & 0.009  &0.06 &   0.06\\
7293    && 2.0  & 0.9    &1.8& 0.2
\\
\hline
\end{tabular}
$$
\end{table}