\begin{table}%t7
%\centering
\par
\caption{Approximate properties of SNR blast waves at the transition into the
pressure-driven snowplough stage for different values of $T_{\rm ISM}$
and $n_{0}$, chosen to demonstrate the
conditions under which SNRs in the pressure-driven snowplough stage
have low Mach number forward shocks which are susceptible to the
radiative overstability. The age of the SNR at the onset of shell
formation, $t_{\rm tr}$, the shock velocity,
$v_{\rm s}$, and the Mach number, $M$, at this time, are given. The values
illustrate that overstable low Mach
number radiative shocks in SNRs will exist.
For $T_{\rm ISM} = 10^{6}\;$K and $n_{0} = 3.5 \times
10^{-3}\;\hbox{${\rm\cm^{-3}~}$}$ the blast wave becomes subsonic before transition to
the pressure-driven snowplough stage.
\label{tab:snrproperties}}
\begin{tabular}{llllll}
\hline\hline
$T_{\rm ISM}$ & $n_{0}$ & $t_{\rm tr}$
& $v_{\rm s}$ & $T_{\rm s}/T_{\rm ISM}$ & $M$ \\
(K) & (${\rm\cm^{-3}}$) & ($10^{5}$~yr) & $(\kmps)$ & & \\
\hline
$2 \times 10^{5}$ & $10^{-3}$ & 11.2 & 115 & 1.7 & 1.7 \\
                  & $10^{-2}$ &  3.3 & 151 & 2.4 & 2.3 \\
                  & $10^{-1}$ &  1.0 & 198 & 3.6 & 3.0 \\
                  & 1 & 0.3 & 260 & 5.6 & 3.9 \\
$10^{6}$ & $10^{-3}$ & 11.2 & 115 & -- & 0.8 \\
         & $10^{-2}$ &  3.3 & 151 & 1.0 & 1.0 \\
         & $10^{-1}$ &  1.0 & 198 & 1.5 & 1.5 \\
         & 1 & 0.3 & 260 & 1.7 & 1.7 \\
\hline
\end{tabular}
\end{table}