\begin{table}%t9
\caption{\label{tab:phnoi}Uncertainty in the $^{12}$C/$^{13}$C ratio caused by the photon
  noise.}
%\centering
\par
\begin{tabular}{c c c}
\hline\hline
 $^{12}$C/$^{13}$C & $S/N$ & $\sigma$ \\
\hline
10 & 100 & $^{\rm -1}_{+2}$ \\
10 & 200 & $^{\rm -1}_{+1}$ \\
10 & 350 & $^{\rm -0}_{+1}$ \\
20 & 100 & $^{\rm -3}_{+5}$ \\
20 & 200 & $^{\rm -2}_{+4}$ \\
20 & 350 & $^{\rm -1}_{+2}$ \\
\hline
\end{tabular}
\end{table}