\begin{table}%t6
\caption{Gas temperature measurements or collision rate constraints.\label{tabtemp}}
%\centerline
{\begin{tabular}{lclccc}
\hline\hline
UT date     & $\langle r_{\rm h}\rangle$ & Molecular lines & \multicolumn{2}{c}{Temperature [K]} &  $x_{\rm ne}^1$ \\[0cm]
[mm/dd.dd]  &   [AU]    &                 & Rotational    &     Kinetic$^1$    &    \\
\hline
\multicolumn{5}{l}{C/1999~T1 (McNaught-Hartley) (2001)}\\
01/06.67    &  1.233    & CH$_3$OH 304/307~GHz & $\rm 52^{+36}_{-16}$ & $\rm 60^{+40}_{-20}$ &   \\
01/30.6--31.2 & 1.395   & HCN(3--2)/(1--0)     & $21.1\pm2.6$	 & 	& $1.2\pm0.4$  \\
01/31.2--31.2 & 1.398   & HCN(3--2)/(1--0)     & $19.4\pm2.0$	 & 	& $0.55\pm0.2$ \\
01/30.5     &  1.400    & CH$_3$OH 157~GHz     & $39\pm 6$        & $38\pm 6$	&           \\
02/05.7--06.1 & 1.448   & HCN(4--3)/(3--2)     & $32\pm7$	 & 	& $\rm 1.4^{+1.8}_{-0.8}$ \\
\multicolumn{5}{l}{C/2001~A2 (LINEAR) (2001)}\\
06/11.7     &  0.855    & CH$_3$OH 157~GHz     & $>$62            & $>$50	&  \\
06/12.8     &  0.863    & CH$_3$OH 145~GHz     & $37\pm26$        & 	& $<$1.1   \\
07/08.2     &  1.143    & HCN(3--2)/(1--0)     & $38\pm 5$	 & 	& $\rm 0.6^{+0.4}_{-0.3}$ \\
07/08.23    &  1.144    & CH$_3$OH 157~GHz     & $56\pm 5$        & $51\pm 5$	&  \\
07/10.2     &  1.169    & HCN(3--2)/(1--0)     & $50\pm 6$	 & 	& $\rm 1.8^{+0.9}_{-0.6}$ \\
\multicolumn{5}{l}{C/2000~WM$_1$ (LINEAR) (2001)}\\
11/24.0     &  1.343    & HCN(3--2)/(1--0)     & $23.7\pm2.3$	 & 	& $0.3\pm0.2$  \\
11/24.8     &  1.329    & HCN(3--2)/(1--0)     & $\rm 58^{+21}_{-13}$ & 	& $\rm 14^{+18}_{-10}$  \\
11/25.4     &  1.320    & CH$_3$OH 157~GHz     & $56\pm 7$        & $50\pm 6$	&  \\
11/25.8     &  1.313    & HCN(3--2)/(1--0)     & $23.0\pm2.7$     & 	& $\rm 0.2^{+0.15}_{-0.1}$  \\
12/03.36    &  1.191    & CH$_3$OH 304/307~GHz & $\rm 36^{+9}_{-7}$   & $\rm 35^{+9}_{-7}$ &  \\
12/05.0     &  1.165    & CH$_3$OH 242~GHz     & $74\pm35$        & $150^{+\infty}_{-80}$ & \\
12/07.7     &  1.121    & HCN(4--3)/(3--2)     & $\rm 51^{+9}_{-7}$   & 	& $\rm 1.5^{+1.3}_{-0.7}$  \\
12/08.0     &  1.116    & CH$_3$OH 304/307~GHz & $\rm 48^{+18}_{-11}$ & $\rm 46^{+17}_{-10}$ &  \\
\multicolumn{5}{l}{153P/Ikeya-Zhang (2002)}\\
03/20.52    &  0.508    & CH$_3$OH 157~GHz     & $99\pm43$        & $75\pm35$ 	&  \\
03/20.6     &  0.508    & HCN(3--2)/(1--0)     & $\rm 67^{+16}_{-11}$ & 	& $\rm 1.4^{+1.8}_{-0.9}$  \\
04/25.59    &  0.977    & CH$_3$OH 251~GHz     & $59\pm 5$        & $72\pm 6$	&  \\
04/27.64    &  1.011    & CH$_3$OH 251~GHz     & $87\pm13$        & $114\pm20$ 	&  \\
04/29.30    &  1.039    & CH$_3$OH 157~GHz     & $62\pm 4$        & $54\pm 4$ 	&  \\
04/30.2     &  1.055    & HCN(3--2)/(1--0)     & $40\pm 3$        & 	& $\rm 0.9^{+0.3}_{-0.2}$  \\
05/09.85    &  1.217    & CH$_3$OH 157~GHz     & $40\pm 7$        & $37\pm 6$ 	&  \\
05/11.34    &  1.242    & CH$_3$OH 157~GHz     & $35\pm 7$        & $32\pm 6$ 	&  \\
05/12.0     &  1.253    & HCN(3--2)/(1--0)     & $31\pm 2$        & 	& $0.9\pm0.2$  \\
05/12.08    &  1.254    & CH$_3$OH 220/254~GHz & $\rm 57^{+13}_{-8}$  & $59\pm10$	&  \\
\hline
\end{tabular}}
\par
\smallskip
$^1$   A constraint on $x_{\rm ne}$ (see text) is given for observations that
do not constraint the kinetic temperature but rather the collision rate.
\end{table}