Brown Dwarf Companions to White Dwarfs
  Brown dwarf companions to white dwarfs are rare, but recent infra-red surveys are slowly reveal- ing examples. We present new observations of the post-common envelope binary WD0137-349, which reveals the effects of irradiation on the ~ 0.05M* secondary, and new observations of GD 1400 which show that it too is a close, post-comon envelope system. We also present the lat- est results in a near-infrared photometric search for unresolved ultracool companions and to white dwarfs with UKIDSS. Twenty five DA white dwarfs were identified as having photometric excesses indicative of a low mass companion, with 8-10 of these having a predicted mass in the range asso- ciated with brown dwarfs. The results of this survey show that the unresolved (< 2") brown dwarf companion fraction to DA white dwarfs is 0.3 \leq fWD+BD \leq 1.3%. 
M.R. Burleigh, P.R. Steele, P.D. Dobbie, J. Farihi, R. Napiwotzki,   P.F.L. Maxted, M.A. Barstow, R.F. Jameson, S.L. Casewel...
astro-ph.EP astro-ph.SR