\begin{table}%t4
\caption{SED fits. \label{SEDfits}}
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%\vspace{-0.3cm}
 %\centerline
{
\begin{tabular}{cccccc}
\hline\hline
\noalign{\smallskip}
Epoch &  Spectral index $\beta$ & $N_{\rm H}^{a}$ [10$^{22}~\rm cm^2$] & $\chi^2$/d.o.f. \\  
\hline
I & 1.00 $\pm$ 0.01 & 0.19 $\pm$ 0.09 & 36/36 \\ 
II & 0.99 $\pm$ 0.01 & 0.17 $\pm$ 0.10 & 15/15 \\ 
III & 1.01 $\pm$ 0.01 & $\rm 0.13 ^{+0.15}_{-0.13}$ & 18/19 \\ 
IV & 1.01 $\pm$ 0.01 & $\rm 0.53 ^{+1.30}_{-0.53}$ & 0.3/3 \\ 
\hline \\
\end{tabular}}
\smallskip
$^{a}$ Intrisic hydrogen column desity, in excess of the frozen Galactic foreground of 
 $N_{\rm H}=4.1\times 10^{20}$~cm$^{-2}$.
\end{table}