\begin{table}%t5
\caption{\label{error}Error sources for the abundances of the chemical elements of 21~Peg.}
%\centerline
{
\begin{tabular}{lrrrrrr}
\hline
\hline
\multicolumn{1}{c}{Ion         }        &  %1
\multicolumn{1}{c}{Abundance   }        &  %2
\multicolumn{1}{c}{$\sigma_{\rm abn}$~(scatt.)}  &  %3
\multicolumn{1}{c}{$\sigma_{\rm abn}$~(\Teff)}  &  %4
\multicolumn{1}{c}{$\sigma_{\rm abn}$~(\logg)}  &  %5
\multicolumn{1}{c}{$\sigma_{\rm abn}$~(\vmic)}  &  %6
\multicolumn{1}{c}{$\sigma_{\rm abn}$~(syst.)}  \\ %7
\multicolumn{1}{c}{            }        & %1
\multicolumn{1}{c}{$\log (N/N_{\rm tot})$} & %2
\multicolumn{1}{c}{(dex)}        & %3
\multicolumn{1}{c}{(dex)}        & %4
\multicolumn{1}{c}{(dex)}        & %5 
\multicolumn{1}{c}{(dex)}        & %6
\multicolumn{1}{c}{(dex)}        \\ %7
\hline
\ion{He}{i }  & $-$1.11 & 0.04 & $-$0.08 &    0.03 &    0.00 & 0.09 \\		 \ion{C}{i}    & $-$3.66 & 0.14 & $-$0.05 & $-$0.13 & $-$0.10 & 0.17 \\		 \ion{C}{ii}   & $-$3.65 & 0.05 & $-$0.17 & $-$0.02 & $-$0.08 & 0.19 \\		 \ion{N}{i}    & $-$3.95 & 0.12 & $-$0.05 & $-$0.07 & $-$0.05 & 0.10 \\		 \ion{N}{ii}   & $-$3.90:&      & $-$0.09 &    0.05 &    0.00 & 0.10 \\		 \ion{O}{i}    & $-$3.28 & 0.11 &    0.00 & $-$0.02 & $-$0.02 & 0.03 \\	      
\ion{Ne}{i}   & $-$3.76 & 0.05 & $-$0.18 & $-$0.03 & $-$0.06 & 0.19 \\	      
\ion{Na}{i}   & $-$5.60 &      &    0.04 & $-$0.04 & $-$0.01 & 0.06 \\	      
\ion{Mg}{i}   & $-$4.42 & 0.12 &    0.10 & $-$0.06 & $-$0.05 & 0.13 \\	      
\ion{Mg}{ii}  & $-$4.56 & 0.03 & $-$0.02 & $-$0.01 & $-$0.02 & 0.03 \\	      
\ion{Al}{i }  & $-$5.89 &      &    0.10 & $-$0.03 &    0.00 & 0.10 \\	      
\ion{Al}{ii}  & $-$5.68 & 0.10 & $-$0.09 &    0.01 & $-$0.03 & 0.10 \\	      
\ion{Si}{i}   & $-$4.95 &      &    0.10 & $-$0.02 &    0.00 & 0.10 \\	      
\ion{Si}{ii}  & $-$4.49 & 0.13 & $-$0.07 &    0.01 & $-$0.03 & 0.08 \\	      
\ion{Si}{iii} & $-$4.26 & 0.18 & $-$0.16 &    0.04 & $-$0.03 & 0.17 \\	      
\ion{P}{ii}   & $-$6.37 & 0.06 & $-$0.08 &    0.02 & $-$0.02 & 0.08 \\	      
\ion{S}{ii}   & $-$4.86 & 0.13 & $-$0.14 &    0.00 & $-$0.05 & 0.15 \\	      
\ion{Ca}{i}   & $-$5.84 & 0.11 &    0.20 & $-$0.07 &    0.00 & 0.21 \\	      
\ion{Ca}{ii}  & $-$5.98 & 0.08 &    0.03 & $-$0.05 & $-$0.04 & 0.07 \\	      
\ion{Sc}{ii}  & $-$9.37 & 0.10 &    0.12 & $-$0.01 &    0.00 & 0.12 \\	      
\ion{Ti}{ii}  & $-$7.23 & 0.09 &    0.08 &    0.00 & $-$0.02 & 0.08 \\	      
\ion{V}{ii}   & $-$7.98 & 0.06 &    0.06 &    0.02 &    0.00 & 0.06 \\	      
\ion{Cr}{i}   & $-$6.29 & 0.09 &    0.13 & $-$0.03 &    0.00 & 0.13 \\	      
\ion{Cr}{ii}  & $-$6.20 & 0.10 &    0.03 &    0.02 & $-$0.01 & 0.04 \\	      
\ion{Mn}{i}   & $-$6.54 & 0.21 &    0.14 & $-$0.03 &    0.00 & 0.14 \\	      
\ion{Mn}{ii}  & $-$6.51 & 0.17 &    0.01 &    0.01 & $-$0.01 & 0.01 \\	      
\ion{Fe}{i}   & $-$4.52 & 0.13 &    0.11 & $-$0.03 &    0.00 & 0.11 \\	      
\ion{Fe}{ii}  & $-$4.50 & 0.12 & $-$0.02 &    0.02 & $-$0.02 & 0.03 \\	      
\ion{Fe}{iii} & $-$4.60 & 0.06 & $-$0.10 &    0.06 & $-$0.01 & 0.12 \\	      
\ion{Co}{ii}  & $-$6.75 & 0.18 &    0.01 &    0.03 &    0.00 & 0.03 \\	      
\ion{Ni}{i}   & $-$5.71 & 0.05 &    0.09 & $-$0.03 & $-$0.01 & 0.10 \\	      
\ion{Ni}{ii}  & $-$5.61 & 0.09 & $-$0.04 &    0.03 & $-$0.01 & 0.05 \\	      
\ion{Zn}{i}   & $-$6.86 &      &    0.10 & $-$0.02 &    0.00 & 0.10 \\	      
\ion{Sr}{ii}  & $-$9.10 & 0.01 &    0.13 & $-$0.03 & $-$0.06 & 0.15 \\	      
\ion{Y}{ii}   & $-$9.76 & 0.15 &    0.13 & $-$0.02 & $-$0.01 & 0.13 \\	      
\ion{Zr}{ii}  & $-$9.48 & 0.28 &    0.11 &    0.00 &    0.00 & 0.11 \\	      
\ion{Ba}{ii}  & $-$9.19 & 0.06 &    0.14 & $-$0.02 & $-$0.01 & 0.14 \\	      
\ion{Nd}{iii} &$-$10.09 & 0.07 &    0.04 &    0.04 &    0.00 & 0.06 \\	      
\hline						\end{tabular}}
\smallskip
\par
Column 3 standard deviation $\sigma_{\rm abn}$ (scatt.) 
of the mean abundance obtained
from different spectral lines (internal scattering); a blank means that the number
of spectral lines is $<$3, hence no internal scattering could be estimated.
(Note that these values are identical to those given in Table~\ref{abundance}.)
Columns 4--6 give the variation in abundance estimated by increasing
\Teff\ by 200~K, \logg\ by 0.1~dex, and \vmic\ by 0.4~km~s$^{-1}$,
respectively. Column~7 gives the the mean error calculated applying the
standard error propagation theory on the systematic uncertainties given in 
Col.~4--6, i.e.,
$\sigma_{\rm abn}^2$~(syst.)~= 
$\sigma_{\rm abn}^2$~(\Teff)  + 
$\sigma_{\rm abn}^2$~(\logg)  + 
$\sigma_{\rm abn}^2$~(\vmic). 
\end{table}