\begin{table}%t3
\caption{\label{error}Error sources for the abundances of the chemical elements in HD~49933.} 
%\centerline
 {\small \begin{tabular}{lrrrrrr}
\hline \hline 
\multicolumn{1}{c}{Ion}  &
\multicolumn{1}{c}{abundance}&\multicolumn{1}{c}{$\sigma_{\rm abn}$~(scatt.)}  &  \multicolumn{1}{c}{$\sigma_{\rm abn}$~(\Teff) }  &  \multicolumn{1}{c}{$\sigma_{\rm abn}$~(\logg) }  &  
\multicolumn{1}{c}{$\sigma_{\rm abn}$~(\vmic) }  &  %6
\multicolumn{1}{c}{$\sigma_{\rm abn}$~(tot)   }  \\ %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)       }        \\\\[-3mm] %7
\hline\\[-3mm]
\ion{C}{i}    & $-$3.74 & 0.10 & $-$0.02 & $ $0.05 & $ $0.00 & 0.11 \\
\ion{O}{i}    & $-$3.55 &      & $-$0.03 & $ $0.05 & $ $0.00 & 0.12 \\
\ion{Na}{i}   & $-$6.15 & 0.05 & $ $0.02 & $ $0.00 & $-$0.01 & 0.05 \\
\ion{Mg}{i}   & $-$4.83 & 0.07 & $ $0.03 & $-$0.01 & $-$0.02 & 0.08 \\
\ion{Mg}{ii}  & $-$4.73 &      & $-$0.02 & $ $0.05 & $-$0.01 & 0.11 \\
\ion{Al}{i}   & $-$6.20 &      & $ $0.02 & $ $0.00 & $ $0.00 & 0.10 \\
\ion{Si}{i}   & $-$4.86 & 0.21 & $ $0.01 & $ $0.00 & $-$0.01 & 0.21 \\
\ion{Si}{ii}  & $-$4.82 & 0.02 & $-$0.03 & $ $0.05 & $-$0.02 & 0.07 \\
\ion{S}{i}    & $-$5.23 & 0.07 & $-$0.01 & $ $0.04 & $ $0.00 & 0.08 \\
\ion{Ca}{i}   & $-$6.01 & 0.11 & $ $0.03 & $-$0.01 & $-$0.05 & 0.12 \\
\ion{Ca}{ii}  & $-$6.01 & 0.09 & $-$0.02 & $ $0.05 & $-$0.01 & 0.11 \\
\ion{Sc}{ii}  & $-$9.24 & 0.12 & $ $0.02 & $ $0.05 & $-$0.05 & 0.14 \\
\ion{Ti}{i}   & $-$7.54 & 0.07 & $ $0.03 & $ $0.00 & $-$0.02 & 0.08 \\
\ion{Ti}{ii}  & $-$7.42 & 0.12 & $ $0.01 & $ $0.05 & $-$0.05 & 0.16 \\
\ion{V}{i}    & $-$8.50 & 0.13 & $ $0.04 & $ $0.00 & $-$0.01 & 0.15 \\
\ion{V}{ii}   & $-$8.47 & 0.23 & $ $0.01 & $ $0.05 & $-$0.01 & 0.15 \\
\ion{Cr}{i}   & $-$6.82 & 0.17 & $ $0.04 & $ $0.00 & $-$0.02 & 0.18 \\
\ion{Cr}{ii}  & $-$6.61 & 0.17 & $ $0.00 & $ $0.05 & $-$0.03 & 0.19 \\
\ion{Mn}{i}   & $-$7.33 & 0.14 & $ $0.03 & $ $0.00 & $-$0.03 & 0.15 \\
\ion{Fe}{i}   & $-$5.04 & 0.06 & $ $0.04 & $-$0.01 & $-$0.04 & 0.13 \\
\ion{Fe}{ii}  & $-$5.03 & 0.08 & $ $0.01 & $ $0.05 & $-$0.05 & 0.12 \\
\ion{Co}{i}   & $-$7.49 & 0.10 & $ $0.03 & $ $0.00 & $ $0.00 & 0.10 \\
\ion{Ni}{i}   & $-$6.34 & 0.10 & $ $0.03 & $ $0.00 & $-$0.02 & 0.11 \\
\ion{Cu}{i}   & $-$8.65 & 0.07 & $ $0.03 & $ $0.00 & $-$0.01 & 0.08 \\
\ion{Zn}{i}   & $-$8.12 & 0.06 & $ $0.02 & $ $0.01 & $-$0.04 & 0.08 \\
\ion{Sr}{i}   & $-$9.65 &      & $ $0.03 & $ $0.00 & $ $0.00 & 0.10 \\
\ion{Sr}{ii}  & $-$9.50 & 0.04 & $ $0.01 & $ $0.06 & $-$0.01 & 0.07 \\
\ion{Y}{ii}   & $-$10.34& 0.10 & $ $0.02 & $ $0.05 & $-$0.02 & 0.12 \\
\ion{Zr}{ii}  & $-$9.85 & 0.06 & $ $0.01 & $ $0.05 & $-$0.01 & 0.08 \\
\ion{Ba}{ii}  & $-$10.06& 0.19 & $ $0.03 & $ $0.02 & $-$0.07 & 0.16 \\
\ion{La}{ii}  & $-$11.21& 0.11 & $ $0.03 & $ $0.06 & $ $0.00 & 0.14 \\
\ion{Ce}{ii}  & $-$10.73& 0.10 & $ $0.03 & $ $0.05 & $ $0.00 & 0.12 \\
\ion{Nd}{ii}  & $-$10.77& 0.28 & $ $0.02 & $ $0.05 & $-$0.01 & 0.28 \\
\ion{Sm}{ii}  & $-$11.09& 0.16 & $ $0.03 & $ $0.05 & $ $0.00 & 0.17 \\
\ion{Eu}{ii}  & $-$11.92& 0.10 & $ $0.03 & $ $0.05 & $ $0.00 & 0.12 \\
\ion{Gd}{ii}  & $-$11.16& 0.09 & $ $0.03 & $ $0.05 & $ $0.00 & 0.15 \\
\ion{Dy}{ii}  & $-$11.36& 0.15 & $ $0.03 & $ $0.05 & $ $0.00 & 0.16 \\
\hline								
\end{tabular}}
\medskip
Column~3 gives the standard deviation $\sigma_{\rm abn}$ (scatt.) 
of the mean abundance obtained from different spectral lines (internal scatter); a blank means that the number of spectral lines is $<$2, hence no internal scatter could be estimated. (Note that these values are identical to those given in Table~\ref{abundance}). Columns~4--6 give the variation in abundance estimated by increasing \Teff\ by 50~K, \logg\ by 0.15~dex, and \vmic\ by 0.2~km~s$^{-1}$, respectively. Column~7 gives the the mean error calculated applying 
standard error propagation theory on the uncertainties given in the
previous columns, i.e.,
$\sigma_{\rm abn}^2$~(tot) = $\sigma_{\rm abn}^2$~(scatt.) + 
$\sigma_{\rm abn}^2$~(\Teff)  + $\sigma_{\rm abn}^2$~(\logg)  + 
$\sigma_{\rm abn}^2$~(\vmic). For the computation of $\sigma_{\rm abn}^2$~(tot) of those ions for which the internal scatter could not be measured, we have assumed a~priori $\sigma_{\rm abn}~{\rm (scatt.)} = 0.10$~dex.
\end{table}