\begin{table}%t1
%\centering
\par
\caption{\label{comp_data}Flux densities and spectral indices of the 
components of the inner double.}
\begin{tabular}{c r r c}
\hline
\hline
Component & \multicolumn{2}{c} {Flux density [mJy]} & Spectral index\\
& 1658~MHz & 4994~MHz & \\
\hline
A1 &     11.7 &  6.2 & 0.57 \\
B1 &      9.9 &  4.4 & 0.75 \\
C1 &     10.9 &  2.3 & 1.40 \\
A2+B2 & 108.6 & 39.1 & 0.93 \\
\hline
\end{tabular}
\end{table}