Quasi-Molecular Lines in Lyman Wings of Cool DA White Dwarfs; Application to FUSE Observations of G 231–40

Abstract

Abstract. We present new theoretical calculations of the total line profiles of Lyman α and Lyman β which include perturbations by both neutral hydrogen and protons and all possible quasi-molecular states of H2 and H + 2 . They are used to improve theoretical modeling of synthetic spectra for cool DA white dwarfs. We compare them with FUSE observation of G 231-40. The appearance of the line wings between Lyman α and Lyman β is shown to be sensitive to the relative abundance of hydrogen ions and neutral atoms, and thereby to provide a temperature diagnostic for stellar atmospheres and laboratory plasmas.