\begin{table}%t13
\caption{\label{t:xcnmodel}Parameters of our best-fit LTE models of methyl cyanide, ethyl cyanide, vinyl cyanide, and aminoacetonitrile, and column density upper limit for cyanomethylidyne.}
\small%\centerline
 {
\begin{tabular}{lccccc}
 \hline\hline
%&&&&& \\[-8pt]
 \multicolumn{1}{c}{Molecule$^{a}$} & \multicolumn{1}{c}{Size$^{b}$} & \multicolumn{1}{c}{$T_{{\rm rot}}$$^{c}$} & \multicolumn{1}{c}{$N^{d}$} & \multicolumn{1}{c}{$\Delta V^{e}$} & \multicolumn{1}{c}{$V_{{\rm off}}$$^{f}$} \\ 
  & \multicolumn{1}{c}{\scriptsize ($''$)} & \multicolumn{1}{c}{\scriptsize (K)} & \multicolumn{1}{c}{\scriptsize (cm$^{-2}$)} & \multicolumn{1}{c}{\scriptsize (km~s$^{-1}$)} & \multicolumn{1}{c}{\scriptsize (km~s$^{-1}$)} \\ 
 \multicolumn{1}{c}{(1)} & \multicolumn{1}{c}{(2)} & \multicolumn{1}{c}{(3)} & \multicolumn{1}{c}{(4)} & \multicolumn{1}{c}{(5)} & \multicolumn{1}{c}{(6)} \\ 
 \hline
%&&&&& \\[-8pt]
CH$_3$CN & 2.7 &  200 & $ 2.00 \times 10^{18}$ & 6.5 & --1.0 \\  & 2.7 &  200 & $ 8.00 \times 10^{17}$ & 6.5 & 9.0 \\  
& 2.7 &  200 & $ 1.00 \times 10^{17}$ & 8.0 & --11.0 \\  
 C$_2$H$_5$CN & 3.0 &  170 & $ 1.20 \times 10^{18}$ & 6.5 & --1.0 \\ 
  & 2.3 &  170 & $ 1.40 \times 10^{18}$ & 6.5 & 9.0 \\
  & 1.7 &  170 & $ 9.00 \times 10^{17}$ & 8.0 & --11.0 \\ 
  C$_2$H$_3$CN & 2.3 &  170 & $ 8.00 \times 10^{17}$ & 7.0 & --1.0 \\
  & 2.3 &  170 & $ 2.40 \times 10^{17}$ & 7.0 & 9.0 \\
  & 2.3 &  170 & $ 1.00 \times 10^{17}$ & 10.0 & --9.0 \\ 
NH$_2$CH$_2$CN & 2.0 &  100 & $ 2.80 \times 10^{16}$ & 7.0 & 0.0 \\ 
\hline
%&&&&& \\[-8pt]
CCN$^g$ & 3.0 &  200 & $<$$1.20 \times 10^{17}$ & 6.5 & --1.0 \\  & 3.0 &  200 & $<$$1.20 \times 10^{17}$ & 6.5 & 9.0 \\  
\hline
\end{tabular}}
\medskip
 Notes: 
 $^a$~We used the JPL entry for CH$_3$CN (version~3), and the CDMS entries for C$_2$H$_5$CN (ver.~1), C$_2$H$_3$CN (ver.~1), NH$_2$CH$_2$CN (ver.~1), and CCN (ver.~1). See references to the laboratory data therein.
 $^b$~Source diameter (\textit{FWHM}).
 $^c$~Temperature.
 $^d$~Column density.
 $^e$~Linewidth (\textit{FWHM}).
 $^f$~Velocity offset with respect to the systemic velocity of Sgr~B2(N) $V_{{\rm lsr}} = 64$~km~s$^{-1}$.
 $^g$~The column density upper limit is $\sim$$3\sigma$. The other parameters were fixed.
\end{table}