\begin{table}%t4
%\centering
\par
\caption{\label{tab-modelpars}Model parameters for the different scenarios as discussed in the text.}
\begin{tabular}{  l  c  c  c}
\hline\hline
\noalign{\smallskip}
\multicolumn{1}{  l  }{Parameter} &
\multicolumn{3}{  c }{Scenario}\\ \cline{2-4}\noalign{\smallskip}
\multicolumn{1}{  c }{} &
\multicolumn{1}{ c  }{I} & 
\multicolumn{1}{ c  }{II} & 
\multicolumn{1}{ c  }{III}\\
\hline
\rs\ [pc] &  $<$0.1 & $0.5$ & $0.225$\\
%\hline
$v_{\rm S}$ [$c$] &
\multicolumn{3}{ c }{$1/3$}\\
%\hline
$\alpha$ &
\multicolumn{3}{ c }{no constraint}\\
%\hline
$\eta$ &
\multicolumn{3}{ c }{0--1}\\
%\hline
$\xi$ &
\multicolumn{3}{ c }{no constraint}\\
\hline
\end{tabular}
\end{table}