\begin{table}%T2
%\centering
\par
\caption{The theoretical
 and observational values of modulation indices,
 logarithmic slopes and refractive timescales.}
         \label{tab2}
	 $$
          \begin{tabular} {cccccccc}
             \hline \hline
      \noalign{\smallskip}
\par
{\parbox[t]{15mm}{\centering
 PSR B}}& {\parbox[t]{8mm}{\centering
\par
$\beta$}}&
 {\parbox[t]{20mm}{\centering
 $m_{{\rm o}}$}}&
{\parbox[t]{8mm}{\centering
  $m_{{\rm t}}$}}&
{\parbox[t]{8mm}{\centering
 $\tau_{{\rm r,o}}$\\(${\rm days}$)}}&
{\parbox[t]{8mm}{\centering
 $\tau_{{\rm r,t}}$\\$({\rm days})$}}&
{\parbox[t]{8mm}{\centering
  $p_{{\rm o}}$}}&
{\parbox[t]{8mm}{\centering
  $p_{{\rm t}}$}}\\
       \noalign{\smallskip}
\hline
      \noalign{\smallskip}
\small \rm
\par
1642--03 & 11/3    & $0.46\pm0.04$  & 0.42  & 0.9 & 0.6 & 0.4 & 0.76 \\
0329+54 & 11/3    & $0.37\pm0.03$  & 0.34  & 15  & 4  & 0.5 & 0.78 \\
0736--40 & 11/3 & $0.03\pm0.006$ & 0.04 & 71  & 128  & 0.7 & 0.77 \\
0740--28 & 11/3 & $0.13\pm0.01$  & 0.12  & 29  & 26  & 0.5 & 0.76 \\
\hline
 \end{tabular}$$
   \end{table}