\begin{table}%t1
%\centering
\par
\caption{Adopted rms errors for the source coordinates, VLBA station
coordinates and Earth Orientation Parameters in our {\it Monte Carlo}
\mbox{simulations}.\label{errors}}
\small
\begin{tabular}{lr} \hline\hline
    Parameters                          &    Errors \\  \hline
    Source coordinates &\\
    $\alpha_0 \cos \delta_0 $           &   0.25/1 mas  \\ 
    $\delta_0$                          &   0.25/1 mas  \\    \hline
    Station coordinates&\\
    $X$                                 &   1--2  mm  \\  
    $Y$                                 &   1--3  mm  \\ 
    $Z$                                 &   1--2  mm  \\   \hline 
    Earth orientation parameters&\\
    $X_{\rm p}$                               &   0.2 mas     \\
    $Y_{\rm p}$                               &   0.2 mas    \\ 
    $UT1-UTC$                           &   0.02 ms \\
    $\psi \sin\epsilon$                 &    0.3 mas    \\
    $\epsilon$                          &    0.3 mas    \\   \hline
\end{tabular}
\end{table}