SPECTROSCOPIC STUDIES OF DB-WHITE-DWARFS - CONFIRMATION AND MODELING OF NEW FORBIDDEN COMPONENTS OF HE-I

Red optical spectrophotometry of three DB white dwarfs confirms the existence, first reported by Greenstein and Liebert, of new forbidden components of He I transitions near 6068 and 6632 Angstrom in the spectra of these stars. However, our search for the additional components tentatively reported earlier near 5379, 6337, and 6485 Angstrom remained unsuccessful. New model atmosphere calculations are presented which strengthen the identification of the confirmed features as, respectively, the forbidden 2 P-3-3 P-3 and 2 P-1-3 P-1 transitions in the He I ion, which arise from Stark perturbations of the upper atomic levels. Our calculations show, furthermore, that these features, which should be generally present in the red spectra of hot DB stars, are predicted with a strength comparable to that observed.