Effect of Silicon Opacity on b- and A-Star Atmospheres

The opacity arising from bound-free transitions for neutral silicon is found to have a significant in- fluence on the emergent fluxes and hydrogen-line profiles for A and late B stars. By ignoring the silicon opacity, effective temperatures and surface gravities are overestimated for silicon-rich stars with Teff ~ 100000 K; for cooler stars the surface gravities are also overestimated. Some simplifications in the dis- cussion of the silicon-rich Ap stars are suggested as a consequence of these results