  SDSS J080531.84+481233.0 is a peculiar L-type dwarf that exhibits unusually
blue near-infrared and mid-infrared colors and divergent optical (L4) and
near-infrared (L9.5) spectral classifications. These peculiar spectral traits
have been variously attributed to condensate cloud effects or subsolar
metallicity. Here I present an improved near-infrared spectrum of this source
which further demonstrates the presence of weak CH4 absorption at 1.6 micron
but no corresponding band at 2.2 micron. It is shown that these features can be
collectively reproduced by the combined light spectrum of a binary with L4.5
and T5 components, as deduced by spectral template matching. Thus, SDSS
J080531.84+481233.0 appears to be a new low-mass binary straddling the L
dwarf/T dwarf transition, an evolutionary phase for brown dwarfs that remains
poorly understood by current theoretical models. The case of SDSS
J080531.84+481233.0 further illustrates how a select range of L dwarf/T dwarf
binaries could be identified and characterized without the need for high
angular resolution imaging or radial velocity monitoring, potentially
alleviating some of the detection biases and limitations inherent to such
techniques.
