Chemical abundances for a sample of southern OB stars

Chemical abundances are presented for carbon, nitrogen, oxygen, magnesium, aluminum, silicon, and sulfur in a sample of 25 OB stars that are members of open clusters, OB associations, and H II regions having Galactocentric distances that lie inside the solar Galactic orbit. The elemental abundances are derived from fits of observed high-resolution spectra to non-LTE synthetic line profiles. Our effective temperature scale is based on calibrations of the Strömgren photometric indices coupled to Hγ line profiles. For stars without Strömgren indices, the reddening-free Q-parameter, defined from UB V photometry is used, with the Q-parameter calibrated against T_eff for stars that have Strömgren photometry. We also investigated other effective temperature scales from the literature and conclude that adoption of these other T_eff scales, which typically result in lower temperatures, produces dependences of the derived abundances with T _eff. Our non-LTE abundances reveal dispersions that are very similar to those expected from the analysis uncertainties. The solar abundances, some of which have been recently revised, fall within the abundance distributions defined by this sample of inner disk OB stars for all seven studied elements.