White Dwarf - Red Dwarf Systems Resolved with the Hubble Space   Telescope: I. First Results
  First results are presented for a Hubble Space Telescope Advanced Camera for Surveys snapshot study of white dwarfs with likely red dwarf companions. Of 48 targets observed and analyzed so far, 27 are totally or partially resolved into two or more components, while an additional 15 systems are almost certainly unresolved binaries. These results provide the first direct empirical evidence for a bimodal distribution of orbital separations among binary systems containing at least one white dwarf. 
J. Farihi, D.W. Hoard, S. Wachter