Observations of normal main-sequence and giant B stars

When interpreting the continuous and line spectra of B stars, it is helpful to think in terms of a model consisting of a photosphere and a mantle which is the outer part of the atmosphere where the effects of nonradiative heating are seen. A survey of the spectra of these stars shows that conditions in the photosphere determine most of what is seen, and in the case of most B stars, the presence of the mantle can be detected only by a special effort. The shape of the visible continuum spectrum and the shape and absolute value of the UV continuous spectrum as determined from low resolution spectra are discussed. Effective temperature for B stars in the main sequence, including corrections for interstellar extinction and bolometric corrections are explored. The major constituents of B-type spectra, variation of the strength of line along the main sequence band, the UV spectra, UV line blocking, intrinsic colors, and variations in light and spectra are also examined.