\begin{table}%T2
\caption{Basic properties and stellar parameters of the sample stars.}
\label{obj}
%\centerline
$${
\begin{tabular}{lr@{$~\pm~$}lr@{$~\pm~$}lr@{$~\pm~$}lr@{$~\pm~$}l}
\hline\hline
& \multicolumn{2}{c}{HD~87737} & \multicolumn{2}{c}{HD~111613} &
\multicolumn{2}{c}{HD~92207} & \multicolumn{2}{c}{HD~34085}\\
\hline
Name & \multicolumn{2}{c}{$\eta$~Leo} & \multicolumn{2}{c}{{\ldots}} &
\multicolumn{2}{c}{{\ldots}} & \multicolumn{2}{c}{$\beta$~Ori, Rigel}\\
Association$^{a}$ & \multicolumn{2}{c}{Field} & \multicolumn{2}{c}{Cen~OB1} & 
\multicolumn{2}{c}{Car~OB1} & \multicolumn{2}{c}{Ori~OB1}\\
Spectral type$^{b}$ & \multicolumn{2}{c}{A0~Ib} & \multicolumn{2}{c}{A2~Iabe} &
\multicolumn{2}{c}{A0~Iae} & \multicolumn{2}{c}{B8~Iae:}\\
$\alpha$~(J2000)$^{b}$ & \multicolumn{2}{c}{10~07~19.95} & 
\multicolumn{2}{c}{12~51~17.98} &
\multicolumn{2}{c}{10~37~27.07} & \multicolumn{2}{c}{05~14~32.27}\\
$\delta$~(J2000)$^{b}$ & \multicolumn{2}{c}{$+$16~45~45.6} &
\multicolumn{2}{c}{$-$60~19~47.2} &
\multicolumn{2}{c}{$-$58~44~00.0} & \multicolumn{2}{c}{$-$08~12~05.9}\\
$l~(\degr)$$^{b}$ & \multicolumn{2}{c}{219.53} & \multicolumn{2}{c}{302.91} &
\multicolumn{2}{c}{286.29} & \multicolumn{2}{c}{209.24}\\
$b~(\degr)$$^{b}$ & \multicolumn{2}{c}{$+$50.75} & \multicolumn{2}{c}{+2.54} & 
\multicolumn{2}{c}{$-$0.26} & \multicolumn{2}{c}{$-$25.25}\\
$\pi$~(mas)$^{c}$ & 1.53 & 0.77 & 1.09 & 0.62 & 0.40 & 0.53 & 4.22 & 0.81\\
$d$~(pc)$^{d}$ & 630 & 90 & 2~290 & 220 & 3~020 & 290 & 360 & 40\\
$R_{\rm g}~(\mbox{kpc})$ & 8.25 & 0.83 & 6.97 & 0.84 & 7.66 & 0.77 & 8.23 & 0.82\\
$\theta_{\rm D}$~(mas)$^{e}$ & \multicolumn{2}{c}{{\ldots}} &
\multicolumn{2}{c}{{\ldots}} & \multicolumn{2}{c}{{\ldots}} & 2.55 & 0.05\\
$v_{\rm rad}~(\mbox{km~s}^{-1})$$^{b}$ & $+$3.3 & 0.9 & 
$-$21.0 & 2.0 & $-$8.5 & 5.0 & $+$20.7 & 0.9\\
$\mu_{\alpha}$~(mas~yr$^{-1}$)$^{c}$ & $-$1.94 & 0.92 & $-$5.26 & 0.55 & $-$7.46
& 0.53 & 1.87 & 0.77\\
$\mu_{\delta}$~(mas~yr$^{-1}$)$^{c}$ & $-$0.53 & 0.43 & $-$1.09 & 0.39 & 3.11 &
0.44 & $-$0.56 & 0.49\\
$U~(\mbox{km~s}^{-1})$ & \multicolumn{2}{c}{4} & \multicolumn{2}{c}{$-$49} & 
\multicolumn{2}{c}{$-$103} & \multicolumn{2}{c}{$-6$}\\
$V~(\mbox{km~s}^{-1})$ & \multicolumn{2}{c}{222} & \multicolumn{2}{c}{211} &
\multicolumn{2}{c}{201} & \multicolumn{2}{c}{214}\\
$W~(\mbox{km~s}^{-1})$ & \multicolumn{2}{c}{6} & \multicolumn{2}{c}{$-$6} &
\multicolumn{2}{c}{$-$6} & \multicolumn{2}{c}{1}\\[2mm]
Atmospheric:\\
$T_{\rm eff}$~(K) & 9600 & 150 & 9150 & 150 & 9500 & 200 & 12~000 & 200\\
$\log g$~(cgs) & 2.00 & 0.15 & 1.45 & 0.10 & 1.20 & 0.10 & 1.75 & 0.10\\
$y$ & 0.13 & 0.02 & 0.105 & 0.02 & 0.12 & 0.02 & 0.135 & 0.02\\
$[$M/H$]$~(dex) & $-$0.04 & 0.03 & $-$0.11 & 0.03 & $-$0.09 & 0.07 & $-$0.06 & 0.10\\
$\xi~(\mbox{km~s}^{-1})$ & 4 & 1 & 7 & 1 & 8 & 1 & 7 & 1\\
$\zeta~(\mbox{km~s}^{-1})$ & 16 & 2 & 21 & 3 & 20 & 5 & 22 & 5\\
$v \sin i~(\mbox{km~s}^{-1})$ & 0 & 3 & 19 & 3 & 30 & 5 & 36 & 5\\[2mm]
Photometric:\\
$V$~(mag)$^{f}$ & \multicolumn{2}{c}{3.52} & \multicolumn{2}{c}{5.72} & 
\multicolumn{2}{c}{5.45} & \multicolumn{2}{c}{0.12}\\
$B-V^{f}$ & \multicolumn{2}{c}{$-$0.03} & \multicolumn{2}{c}{+0.38} &
\multicolumn{2}{c}{+0.50} & \multicolumn{2}{c}{$-$0.03}\\
$U-B^{f}$ & \multicolumn{2}{c}{$-$0.21} & \multicolumn{2}{c}{$-$0.10} &
\multicolumn{2}{c}{$-$0.24} & \multicolumn{2}{c}{$-$0.66}\\
$E(B-V)$ & \multicolumn{2}{c}{0.02} & \multicolumn{2}{c}{0.39} &
\multicolumn{2}{c}{0.48$^{g}$} & \multicolumn{2}{c}{0.05}\\
$(m-M)_0^{d}$ & 9.0 & 0.3 & 11.8 & 0.2 &
12.4 & 0.2 & 7.8 & 0.2\\
$M_V$ & $-$5.54 & 0.3 & $-$7.29 & 0.2 &
$-$8.82 & 0.2 & $-$7.84 & 0.2\\
$B.C.$ & \multicolumn{2}{c}{$-$0.29} & \multicolumn{2}{c}{$-$0.23}
& \multicolumn{2}{c}{$-$0.34} & \multicolumn{2}{c}{$-$0.78}\\
$M_{\rm bol}$ & $-$5.83 & 0.3 & $-$7.52 & 0.2 &
$-$9.16 & 0.2 & $-$8.62 & 0.2\\[2mm]
Physical:\\
$\log L/L_{\odot}$ & 4.23 & 0.12 & 4.90 & 0.08 & 
5.56 & 0.08 & 5.34 & 0.08\\
$R/R_{\odot}$ & 47 & 8 & 112 & 12 &
223 & 24 & 109 & 12\\
$M/M_{\odot}^{\rm ZAMS}$ & 10 & 1 & 16 & 1 &
30 & 3 & 24 & 3\\
$M/M_{\odot}^{\rm evol}$ & 10 & 1 & 15 & 1 &
25 & 3 & 21 & 3\\
$M/M_{\odot}^{\rm spec}$ & 8 & 4 & 13 & 4 &
29 & 10 & 24 & 8\\
$\tau_{\rm evol}$~(Myr) & 25 & 5 & 14 & 2 & 7 & 1 & 8 & 1\\
\hline
\end{tabular} }
$$
\smallskip
$^{a}$~Blaha \& Humphreys~(\cite{BlHu89});
$^{b}$~adopted from the Simbad database at CDS;
$^{c}$~Perryman et~al. (\cite{Perrymanetal97});
$^{d}$~see text;
$^{e}$~Hanbury Brown et~al. (\cite{HanburyBrownetal74});
$^{f}$~Nicolet (\cite{Nicolet78});
$^{g}$~with $R_V$~$=$~3.9, see Sect.~\ref{spectrophotometry}.
\end{table}