\begin{table}%t4
\caption{\label{tab:fitres}Best-fit parameters from the \lya\ line fitting. Values marked in bold face have been fixed during the fitting procedure.}
\par
%\centering
\par
\begin{tabular}{lllllll}
\hline 
\hline\noalign{\smallskip}
Param. & {\tt zsys\_V400} & {\tt zsys\_V500}  & {\tt zsys} & {\tt V400} & {\tt V500} & {\tt free} \\
\hline\noalign{\smallskip}
$n({\rm HI})$ [cm$^{-2}$]       & 20.8      & 20.8      & 20.8  & 20.8     & 21.4      &   $\rm 21.4^{+0.0}_{-0.6}$  \\
$V_{\rm exp}$  [km~s$^{-1}$]     & {\bf 400} & {\bf 500} & 500   & {\bf 400}& {\bf 500} &$\rm 500^{+0}_{-201}$\\
$\tau_{\rm a}$                  & 3.0       & 3.0        & 3.0  & 3.0       & 3.0       &$\rm 3.0^{1.0}_{-2.0}$     \\
$b$              [km~s$^{-1}$]     & 10.0      & 40.0       & 40.0 & 20.0     & 10.0      & $\rm 10.0_{-0.0}^{+150.0}$    \\
$z$                             & {\bf 5.553} & {\bf 5.553} & {\bf 5.553}&5.551  & 5.540   & $\rm 5.540^{+0.007}_{-0.001}$ \\
$\chi^2_\nu$                    & 3.97         & 3.22       & 3.22  & 3.19    & 1.785   &1.785 \\[2pt]
\hline
\end{tabular}
\end{table}