  Planetary systems commonly survive the evolution of single stars, as
evidenced by terrestrial-like planetesimal debris observed orbiting and
polluting the surfaces of white dwarfs. This letter reports the identification
of a circumbinary dust disk surrounding a white dwarf with a substellar
companion in a 2.27 hr orbit. The system bears the dual hallmarks of
atmospheric metal pollution and infrared excess, however the standard (flat and
opaque) disk configuration is dynamically precluded by the binary. Instead, the
detected reservoir of debris must lie well beyond the Roche limit in an
optically thin configuration, where erosion by stellar irradiation is
relatively rapid. This finding demonstrates that rocky planetesimal formation
is robust around close binaries, even those with low mass ratios.
