\begin{table}%t6
\caption {\label{table:6}Numerical amplitudes of the fitted terms (i.e constant term, secular term, 18.6-yr and 9.3-yr nutation terms) for the VLBI series.} % title of Table
%\centering
 % used for centering table
\begin{tabular}{c r r} % centered columns (4 columns)
\hline\hline % inserts double horizontal lines
Terms & $DX$ (mas)  & $DY$ (mas)  \\ % table heading
\hline % inserts single horizontal line
sin (18.6-yr) & $ 0.000\pm 0.004$  & $ 0.013\pm 0.004$ \\
cos (18.6-yr) & $ 0.060\pm 0.004$  & $ -0.067\pm 0.004$ \\
sin (9.3-yr)  & $ -0.004\pm 0.003$  & $-0.000\pm 0.003$ \\
cos (9.3-yr)  & $ 0.011\pm 0.003$  & $ -0.005\pm 0.003$ \\ 
secular term (mas/cy) & $0.054 \pm 0.067$ & $-0.118 \pm 0.067$ \\
constant term & $0.044 \pm 0.002$ & $-0.101 \pm 0.002$ \\
\hline %inserts single line
\end{tabular}
\end{table}