Table 1: Stellar parameters of the selected O stars. Spectral types are from Walborn (1973,1976). Hipparcos parallaxes were taken from Perryman et al. (1997). All other parameters were taken from the "preferred solution'' (some stars have more than one possible set of parameters that fits the observations) of Markova et al. (2004), except for 10 Lac, for which we used Mokiem et al. (2005). We show both the distance from Hipparcos and the distance used for the spectral modeling. As this latter value is used to determine the mass-loss rates, this distance was also used for predicting the thermal radio flux. For the preferred solutions of Markova et al. (2004), we have scaled the distance from the original solution using the absolute magnitudes, as the reddening is assumed to be the same for both solutions.
  $\xi $ Per $\alpha $ Cam 15 Mon $\lambda $ Cep 10 Lac
HD number 24912 30614 47839 210839 214680
Association/Runaway Runaway Runaway Mon OB1 Runaway Lac OB1
Spectral type O7.5III(n)((f))a O9.5 Ia O7 V ((f)) O6 I (n)fp O9 V
Parallax (mas) $1.84\pm0.70$ $0.47\pm0.60$ $3.09\pm0.53$ $1.98\pm0.46$ $3.08\pm0.62$
Hip. distance (pc) $\rm 540^{+330}_{-150}$ >440 $\rm 323^{+67}_{-47}$ $\rm 510^{+150}_{-100}$ $\rm 320^{+90}_{-50}$
Spectral mod. distance (pc) 895 765 710 1089 320
Mass (${M}_\odot$) 52 22 25 58 27
Radius (${R}_\odot$) 25.2 19.6 9.9 23 8.3
$T_{\rm eff}$ (103 K) 34.0 31.0 37.5 36.2 36.0
Luminosity ( $10^5~{L}_\odot$) 7.6 3.2 1.7 8.1 1.0
Terminal velocity (km s-1) 2400 1550 2200 2200 1140
Mass-loss ( $10^{-6}~M_\odot$ y-1) $4.0 \pm 1.0$ $2.9\pm0.9$ $1.2\pm0.3$ $7.7\pm2.3$ $6.1^{+8.8}_{-5.5} \times 10^{-2}$
a This is the spectral type given by Walborn (1973), however, a spectral type of O7.5I(n)((f))
was adopted by Markova et al. (2004).

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