Some comments on the Balmer line emission from Be stars

A simplified Stromgren-sphere model is developed for the atmosphere of the Herbig Be star HD 200775 on the basis of high-resolution optical spectra (Baschek et al., 1982). The gas density and envelope volume are determined from the Balmer decrement: the spherical envelope has density greater than about 10 to the 8th/cu cm and a radius as large as 100 stellar radii, and its temperature is assumed to be about 10,000 K. These results are found to be consistent with model calculations for Stromgren-type sphere about a 14,000-K blackbody ('normal B-type') star producing 1000 times more Balmer-continuum photons than Lyman-continuum photons. Similar calculations are presented for a B supergiant, and graphs illustrating the most significant parameter relations are provided.