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

Theoretical Lyman alpha absorption profiles show a significant dependence on temperature of the H-2 satellite at 1600 Angstrom, whereas the H-2(+) satellite at 1400 Angstrom remains 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 a profiles over the ZZ Ceti range of temperatures have been used to synthesize theoretical spectra which compare very well to existing HST spectra.