\begin{table}%t4
\caption{\label{VLBIfluxes}\label{VLAfluxes}Spectral indices, $\alpha$, determined from our VLA data
for a subset of observations for which we have quasi-simultaneous
6 and 18~cm observations (M~81 used as calibrator).}
 \small
%\centerline
{
\begin{tabular}{c|c}
\hline\hline
Age (days) &$\alpha$\\
 \hline
2794  & $0.68\pm0.01$ \\
2820$^a$ 
&  $ 0.67\pm0.02$ \\
3511 & $0.555\pm0.010$ \\
3858 & $0.50\pm0.04$ \\
\hline
\end{tabular}}
\smallskip
$^a$ {From P\'erez-Torres et~al. (\cite{PerezTorres2002}).} 
\end{table}