Identification of 13 DB + dM and 2 DC + dM binaries from the Sloan   Digital Sky Survey
  We present the identification of 13 DB + dM binaries and 2 DC + dM binaries from the Sloan Digital Sky Survey (SDSS). Before the SDSS only 2 DB + dM binaries and 1 DC + dM binary were known. At least three, possibly 8, of the new DB + dM binaries seem to have white dwarf temperatures well above 30000 K which would place them in the so called DB-gap. Finding these DB white dwarfs in binaries may suggest that they have formed through a different evolutionary channel than the ones in which DA white dwarfs transform into DB white dwarfs due to convection in the upper layers. 
E.J.M. van den Besselaar (1), G.H.A. Roelofs (1), G.A. Nelemans (1),   T. Augusteijn (2), P.J. Groot (1) ((1) Nijmegen, The ...