Binaries among Ultra-cool Dwarfs and Brown Dwarfs
  Observations of brown dwarfs provide important feedback on theories of atmospheres and inner structure of substellar objects. Brown dwarf binary systems furthermore offer the unique opportunity to determine the mass of individual brown dwarfs, which is one of the fundamental astrophysical quantities. 
Wolfgang Brandner (MPIA), Herve Bouy (MPE), Eduardo L. Martin (IAC),   Stefan Umbreit (MPIA)