Chemical abundances in early-type stars. III. NLTE temperature and gravity determination.

Effective temperatures Teff and gravities log g of l9 unevolved B stars in the local field and nearby associations are given. Determinations of Teff due to non-LTE analyses of silicon line formation and non-LTE analyses of helium line formation are compared, and a reasonable agreement is obtained. Small differences were observed for four B stars only. The temperature calibration of some important photometric observables is discussed, with particular emphasis on a comparison with synthetic spectral indices. Temperatures obtained from the nonthermodynamic ionization equilibria of helium and silicon were found to be systematically higher by 2000 K than those calculated from synthetic photometry and LTE assumptions.