A search for hidden white dwarfs in the ROSAT EUV survey II: Discovery   of a distant DA+F6/7V binary system in a direction of low density neutral   hydrogen
  We report the results of our final search for hot white dwarfs in unresolved, Sirius-type, binary systems with IUE. One new system, RE J0500-364 (DA+F6/7V), has been identified. This star appears to lie at a distance of between 500-1000pc, making it one of the most distant white dwarfs, if not the most distant, to be detected in the EUV surveys. The very low line-of-sight neutral hydrogen volume density to this object could place a lower limit on the length of the Beta CMa interstellar tunnel of diffuse gas, which stretches away from the Local Bubble in a similar direction to RE J0500-364. 
M.R. Burleigh, M.A. Barstow (University of Leicester) and J.B. Holberg   (University of Arizona)