2003A&A...405.1153H

We present new theoretical calculations of the line profile of Lyman γ that include transitions in which a photon is absorbed by a neutral hydrogen atom while it interacts with a proton. Models show that two absorption features located near 992Å and 996Å are due to H-H⁺ collisions. These quasi-molecular satellites are similar to those that were identified in the wings of Lyman α and Lyman β lines of hydrogen-rich white dwarfs. We compute synthetic spectra that take account of these new theoretical profiles and compare them to the spectra of four DA white dwarfs that were observed with FUSE. The models predict the absorption features that are observed in the wing of Lyman γ near 995Å, and confirm that these features are quasi-molecular satellites.