\begin{table}%t6
\caption{\label{tab:rm}RM of the core (Col.~3) and jet component (Col.~4).}
%\centerline
 {\small   \begin{tabular}{cccc}
\hline \hline\noalign{\smallskip}
& Epoch & $RM_{\rm core}$ [rad/${\rm m}^2$] & $RM_{\rm jet}$ [rad/${\rm m}^2$] \\
\hline
A & 2007.540 & $-501 \pm 107$ & $-65 \pm 16$\\ 
B & 2007.661 & $-90 \pm 29$ & $(83 \pm 159)$ $^a$ \\ 
C & 2007.773 & $15 \pm 46$ & $(121 \pm 46)$$^a$ \\ 
D & 2007.907 & $30 \pm 1$ & $181 \pm 28$ \\ 
E & 2008.025 & $-48 \pm 51$ & $128 \pm 127$ \\ 
F & 2008.137 & $-141 \pm 23$ & $(86 \pm 61)$$^a$  \\
\hline
\end{tabular}}
\medskip
$^a$ The values in parentheses are based upon only two frequency measurements.
\end{table}