  High-resolution imaging has revealed an unusually high binary fraction
amongst objects spanning the transition between the L dwarf and T dwarf
spectral classes. In an attempt to reproduce and unravel the origins of this
apparent binary excess, I present a series of Monte Carlo mass function and
multiplicity simulations of field brown dwarfs in the vicinity of the Sun.
These simulations are based on the solar metallicity brown dwarf evolutionary
models and incorporate empirical luminosity and absolute magnitude scales,
measured multiplicity statistics and observed spectral templates in the
construction and classification of composite binary spectra. In addition to
providing predictions on the number and surface density distributions of L and
T dwarfs for volume-limited and magnitude-limited samples, these simulations
successfully reproduce the observed binary fraction distribution assuming an
intrinsic (resolved) binary fraction of 11(+6)(-3)% (95% confidence interval),
consistent with prior determinations. However, the true binary fraction may be
as high as 40% if, as suggested by Liu et al., a significant fraction of L/T
transition objects (~66%) are tightly-bound, unresolved multiples. The
simulations presented here demonstrate that the binary excess amongst L/T
transition objects arises primarily from the flattening of the luminosity scale
over these spectral types and is not inherently the result of selection effects
incurred in current magnitude-limited imaging samples. Indeed, the existence of
a binary excess can be seen as further evidence that brown dwarfs traverse the
L/T transition rapidly, possibly driven by a nonequilibrium submergence of
photospheric condensates.
