A study of the Lyman-$\alpha$ line profile in DBA white dwarfs
  The hydrogen abundances in DBA white dwarfs determined from optical or UV spectra have been reported to differ significantly in some studies. We revisit this problem using our own model atmospheres and synthetic spectra, and present a theoretical investigation of the Lyman-$\alpha$ line profile as a function of effective temperature and hydrogen abundance. We identify one possible solution to this discrepancy and show considerable improvement from a detailed analysis of optical and UV spectra of DBA stars. 
C. Genest-Beaulieu and P. Bergeron
astro-ph.SR