\begin{table}%t7
\caption{Model parameters used.\label{tabmod}}
%\centerline
{
\begin{tabular}{lcrcclc}
\hline\hline
  UT date & $\langle r_{\rm h}\rangle$ & Temperature & $v_{\rm exp}$ & $\beta_0$(HCN)& \multicolumn{2}{c}{$Q_{\rm H_2O}$} \\[0cm]
[mm/dd--dd]  &  [AU]  & in the coma & [km~s$^{-1}$] & [s$^{-1}$]    & [molec~s$^{-1}$] & (Ref.) \\
\hline
\multicolumn{6}{l}{C/1999~T1 (McNaught-Hartley) (2000/2001)}\\
 09/28-30    & 1.64   &  40 K       & 0.65          & $1.91\times10^{-5}$ & $4.0\times10^{28}$ & (1) \\
 01/03-07    & 1.23   &  55 K       & 0.70          & $1.80\times10^{-5}$ & $9.0\times10^{28}$ & (1) \\
 01/24-30    & 1.37   &  50 K       & 0.70          & $1.75\times10^{-5}$ & $6.5\times10^{28}$ & (1) \\
 02/00-02    & 1.41   &  45 K       & 0.70          & $1.71\times10^{-5}$ & $6.0\times10^{28}$ & (1) \\
 02/04-07    & 1.45   &  45 K       & 0.65          & $1.72\times10^{-5}$ & $5.5\times10^{28}$ & (1) \\
\multicolumn{6}{l}{C/2001~A2 (LINEAR) (2001)}\\
 06/06       & 0.82   &  70 K       & 0.85          & $1.75\times10^{-5}$ & $1.0\times10^{29}$ & (2) \\
 06/11-12    & 0.86   &  70 K       & 0.85          & $1.80\times10^{-5}$ & $1.5\times10^{29}$ & (2,3) \\
 06/16       & 0.90   &  65 K       & 0.85          & $2.00\times10^{-5}$ & $1.2\times10^{29}$ & (2,3) \\
 06/17-19    & 0.92   &  60 K       & 0.80          & $2.00\times10^{-5}$ & $0.8\times10^{29}$ & (2) \\
 07/08-10    & 1.16   &  50 K       & 0.70          & $1.62\times10^{-5}$ & $0.4\times10^{29}$ & (2) \\
\multicolumn{6}{l}{C/2000~WM$_1$ (LINEAR) (2001)}\\
 11/23-27    & 1.33   &  50 K       & 0.65          & $1.80\times10^{-5}$ & $2.5\times10^{28}$ & (4) \\
 12/03-04    & 1.19   &  55 K       & 0.70          & $2.07\times10^{-5}$ & $3.7\times10^{28}$ & (4) \\
 12/05-08    & 1.14   &  60 K       & 0.70          & $2.05\times10^{-5}$ & $4.0\times10^{28}$ & (4) \\
\multicolumn{6}{l}{153P/Ikeya-Zhang (2002)}\\
 03/19-20    & 0.508  & 120 K       & 1.20          & $1.84\times10^{-5}$ & $7.0\times10^{29}$ & (5) \\
 04/24-25    & 0.96   &  63 K       & 0.88          & $1.75\times10^{-5}$ & $2.1\times10^{29}$ & (6) \\
 04/26-28    & 1.01   &  60 K       & 0.85          & $1.75\times10^{-5}$ & $1.8\times10^{29}$ & (6) \\
 04/29-30    & 1.05   &  55 K       & 0.82          & $1.71\times10^{-5}$ & $1.6\times10^{29}$ & (6) \\
 05/08-09    & 1.19   &  50 K       & 0.75          & $1.87\times10^{-5}$ & $1.0\times10^{29}$ & (6) \\
 05/11-12    & 1.25   &  48 K       & 0.75          & $1.87\times10^{-5}$ & $0.8\times10^{29}$ & (6) \\
\hline
\end{tabular}}
\par
\smallskip
(1) From power law fit: $17.3\times10^{28}r_{\rm h}^{-3.1}$ based on SWAS H$_2$O observations (\cite{Ben04} 2004). \\
(2) From a power law fit $6.8\times10^{28}r_{\rm h}^{-2}$ based on \cite{Lec03} (2003) and \cite{Hja05} (2005). \\
(3) Outburst from \cite{Cro02} (2002). \\
(4) From \cite{Lec03} (2003) assuming $r_{\rm h}^{-2}$ dependence:  $5.2\times10^{28}r_{\rm h}^{-2}$ molec~s$^{-1}$.\\
(5) From \cite{Del04} (2004). \\
(6) Power law fit $19.0\times10^{28}r_{\rm h}^{-4}$ based on \cite{Lec03} (2003) (Fig.~\ref{figqpiz}).
\end{table}