\begin{table}%t3
\caption{\label{onc_parameters}Final stellar parameters and metallicity values derived for ONC 
stars$^1$.}
%%\centerline

{\begin{tabular}{ccccccrr}
\hline\hline
Star     & $r$  & $T_{\rm eff}$  &  $\log~g$ & $\xi$ & $v\sin i$ & \multicolumn{2}{c}{[Fe/H] $\pm$ $\sigma_1$ $\pm$ $\sigma_2$} \\
   &         & (K) &  & (km~s$^{-1}$) & (km~s$^{-1}$) & ($EW$s) & (Spec. Synth.)\\
 (1) & (2) & (3)  & (4)  & (5)  &  (6)  & (7) & (8) \\
\hline
223a &  $0.02 \pm 0.04$ & 4450    & 3.8 & 1.6 & --- & $0.03\pm0.06\pm 0.07$ (18)& ---\\
268  &  $0.03 \pm 0.04$ & 4300    & 3.9 & 1.6 & $10~\pm~3$ & $-0.08\pm 0.16\pm 0.09$ (25)& $-0.1\pm 0.1\pm 0.1$\\
278  &  $0.8  \pm 0.07$ & 4395    & --- & --- &--- & --- & ---\\
487  &  $0.02 \pm 0.02$ & 4300    & 3.9 & 1.7 & $15~\pm~3$ & $-0.07\pm 0.08\pm 0.09$ (18) & $0\pm 0.1\pm 0.09$\\
673  &  $ 0.04 \pm 0.03$ & 4700   & 4.0 & 1.5$^*$ & $20~\pm~3$ & $0.0\pm 0.1\pm 0.07$ (18)& $0\pm 0.1 \pm 0.08$\\
683  &  $ 0.0 \pm 0.02$ & 4250    & 3.3 & 1.6 & $13~\pm~3$ & $0.01\pm 0.1\pm 0.08$ (22) & $-0.1\pm 0.1 \pm 0.09$\\
907  &  $0.01 \pm 0.03$ & 4775    & 4.1 & 1.5 & $35~\pm~3$ & --- & $0.0\pm 0.1 \pm 0.11$\\
     &       &     &  &  & & & \\
664  &  0$^{**}$ &     4200	 & 4.1 & 1.6 & 13~$\pm~3 $ & --- & $0.05\pm 0.1\pm 0.1$\\
1020 & 0$^{**}$ &      4200	& 3.8 & 1.6 & 13~$\pm~3$ & --- & $0.0\pm 0.1\pm 0.1$\\
     &     &      		&   &  & & & \\
VXR76A (list$_{\rm CD3}$)& --- &      4340 & 4.5  & 1.2  & $8~\pm~3$ & $0.00\pm 0.06 \pm 0.09$ (25) & $0 \pm 0.1\pm 0.1$\\
VXR76A (list$_{\rm CD4}$)& --- &      4400	 & 4.5  & 1.3 & $8~\pm~3$ & $-0.01\pm 0.08\pm 0.08$ (23)& $0\pm 0.1\pm 0.1$\\\hline 
\end{tabular}} 
 ${^*}$ The initial microturbulence was adopted
for this star, since $\xi$ could not be optimized due to the lack of  lines covering a wide enough $EW$ interval.
\par
 ${^{**}}$ $r$ values for stars 664 and 1020 come from Palla
et al.~(\cite{pal05}).\\	     
$^{1}$ {In the table we list
the star ID, the veiling $r$, adopted stellar parameters,
projected rotational velocities, and the final
[Fe/H] values, from the $EW$ and synthesis analysis,
along with $\sigma_1$ and $\sigma_2$ errors (see text).
For [Fe/H] from $EW$s we also provide in parenthesis the 
number of employed Fe~I lines.}
\end{table}