Temperature dependence of the Lyman αline wings in cool hydrogen-rich white dwarf atmospheres. Application to ZZ Ceti white dwarf spectra

Theoretical Lyman α absorption profiles show a significant dependence on temperature of the H2 satellite at 1600 Å, whereas the H satellite at 1400 Åremains unchanged. The use of opacities calculated with different approximations concerning the electric dipole transition moment (constant, dependent on interatomic distance, and modulated by the Boltzmann factor) lead to very different synthetic absorption spectra. Our new Lyman α profiles over the ZZ Ceti range of temperatures have been used to synthesize theoretical spectra which compare very well to existing HST spectra.