\begin{table}%t2
\caption{\label{chi2}Significance for intra-orbital flux modulation by fitting the light curves of different phase bins against a constant by using the $\chi^{2}$ test statistics, including the best-fit mean levels.}
%\centering
\par
\begin{tabular}{cccc}
    \hline \hline
      Number of bins & Mean level & $\chi^{2}_{\nu}$ & Significance(\%) \\\hline\\[-1.5ex]
      10 &  $37.1\pm2.7$ & 2.22 & 98.2 \\[+0.5ex] 
      11 &  $33.4\pm2.4$ & 1.82 & 94.8 \\[+0.5ex]
      12 &  $29.6\pm2.1$ & 1.62 & 91.2 \\[+0.5ex]
      13 &  $28.6\pm2.1$ & 2.38 & 99.6 \\[+0.5ex]
      14 &  $26.4\pm2.0$ & 1.86 & 97.0 \\[+0.5ex]
      15 &  $24.7\pm1.9$ & 2.01  & 98.7 \\[+0.5ex]
      20 &  $18.4\pm1.1$ & 1.34 & 89.0 \\[+0.5ex]
      40 &  $9.2\pm0.5$  & 1.25  & 88.5 \\[+0.5ex]
\hline
\end{tabular}
\end{table}