An analysis of metallic high ion absorption line profiles at DA white   dwarfs with circumstellar material
  Some hot DA stars exhibit circumstellar absorption in the metal resonance lines in their spectra. In many cases, these circumstellar features are unresolved from those originating in the photosphere. To better understand the effect this circumstellar blending has on photospheric abundance estimates, we present here an analysis of the unresolved metal high ion absorption features of six hot white dwarfs. In all cases, given the strong circumstellar C IV detections, the photospheric C IV abundances are reduced; conversely the weak circumstellar Si IV leads to modest photospheric abundance revisions. A possible new technique for modelling these line profiles is discussed, that can better reproduce the observations and provide a greater insight into the conditions of the circumstellar medium. 
Nathan J. Dickinson, Martin A. Barstow, and Barry Y. Welsh
astro-ph.SR