\begin{table}%t2
%\centering
\par
\caption
         {Photon luminosity for a neutron star with $T_{\rm core}= 10^7$~K.
         \label{ta:lum_7}}
\begin{tabular}{ccc}
\hline\hline
$B$[G]      &     $L$[erg/s]        &   $L$[erg/s]       \\
          &    Isothermal       &   Crustal        \\
          &       crust         &   field          \\
\hline
10$^{12}  $ & $2.84\times 10^{30}$ &  $2.62\times 10^{30}$\\
10$^{12.5}$ & $3.46\times 10^{30}$ &  $2.38\times 10^{30}$\\
10$^{13}  $ & $1.00\times 10^{31}$ &  $2.00\times 10^{30}$\\
\hline
\end{tabular}
\end{table}