\begin{table}%t1
\caption{\label{table parameters}Parameters of Cyg~OB2 No.~8A used in this work.}
%\centerline
{\small
\begin{tabular}{llllll}
\hline\hline
Parameter & Primary & Secondary \\
\hline
$T_{\rm eff}$ (K)                & 36~800 & 39~200 \\
$R_*$ ($R_{\odot}$)                 & 20.0  & 14.8 \\
$M_*$ ($M_{\odot}$)                 & 44.1  & 37.4 \\
log $L_{\rm bol}/L_{\odot}$         & 5.82  & 5.67 \\
$\dot{M}$ ($M_{\odot}~ {\rm yr}^{-1}$) & $4.8 \times 10^{-6}$ & $3.0 \times 10^{-6}$ \\
$\varv_\infty$ (km s$^{-1}$)           & 1873  & 2107  \\
semi-major axis $a$ ($R_{\odot}$) & 65.7 & 76.0 \\
period $P$ (days)  & \multicolumn{2}{c}{$21.908 \pm 0.040$} \\
eccentricity $e$   & \multicolumn{2}{c}{$0.24 \pm 0.04$} \\
inclination $i$    & \multicolumn{2}{c}{$32\degr \pm 5\degr$} \\
distance $D$ (kpc) & \multicolumn{2}{c}{1.8} \\
\hline
\end{tabular}}
\tablefoot{These parameters were derived by \citet{2006MNRAS.371.1280D}.}
\end{table}