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Arguably, the best method for determining the effective temperature($T_{\mathrm{eff}}$) and surface gravity (log $g$) of a DA white dwarf is byfitting the Hydrogen Lyman and Balmer absorption features. However, as has beenshown for white dwarfs with $T_{\mathrm{eff}}$>50,000K, the calculated valuefrom the Lyman and Balmer lines are discrepant, which worsens with increasingtemperature. Many different solutions have been suggested, ranging from theinput physics used to calculate the models, to interstellar reddening. We willfocus on the former, and consider three variables. The first is the atomic dataused, namely the number of transitions included in line blanketing treatmentsand the photoionization cross sections. The second is the stark broadeningtreatment used to synthesise the Lyman and Balmer line profiles, namely thecalculations performed by Lemke (1997) and Tremblay & Bergeron (2009). Finally,the third is the atmospheric content. The model grids are calculated with apure H composition, and a metal polluted composition using the abundances ofPreval et al. (2013). We present the preliminary results of our analysis,whereby we have determined the $T_{\mathrm{eff}}$ for a small selection ofwhite dwarfs. We plan to extend our analysis by allowing metallicity to vary infuture model grids.

A possible solution to the Lyman/Balmer line problem in hot DA white dwarfs