Quantitative studies of the optical and UV spectra of Galactic early B supergiants - I. Fundamental parameters

摘要: Aims. We undertake an optical and ultraviolet spectroscopic analysis of a sample 20 Galactic B0-B5 supergiants luminosity classes Ia, Ib, Iab, II. Fundamental stellar parameters are obtained from diagnostics critical comparison the model predictions to observed UV spectral features is made. Methods. (e.g., ${T_{\rm eff}}$, ${\rm log L_{*}}$, mass-loss rates CNO abundances) derived for individual stars using CMFGEN, nLTE, line-blanketed atmosphere code. The impact these newly on Galactic B supergiant eff}}$ scale, mass discrepancy, wind-momentum relation examined. Results. B supergiant temperature scale here shows reduction about 1000-3000 K compared previous results unblanketed codes. Mass-loss rate estimates in good agreement with predicted theoretical values, all 20 B0-B5 supergiants analysed show evidence CNO processing. A discrepancy still exists between evolutionary masses, largest occurring at log\ (L/L_{\odot}})$ ~ 5.4. WLR values calculated B0-B0.7 supergiants higher than whereas reverse true B1-B5 supergiants. This means that cannot be resolved by adopting clumped (i.e., lower) as O stars. most surprising result that, although CMFGEN succeeds reproducing spectrum accurately, it fails precisely reproduce key UV diagnostics, such $\ion{N}{v}$ $\ion{C}{iv}$ P Cygni profiles. problem arises because models not ionised enough fail full extent absorption trough P Cygni profiles. Conclusions. Newly-derived fundamental early B supergiants similar work field. significant discovery, however, failure predict correct ionisation fraction some ions. Such findings add further support revising current standard massive star winds, our understanding winds incomplete without precise knowledge structure distribution clumping wind.