  Evidence is presented that 2MASS J03202839-0446358, a late-type dwarf with
discrepant optical (M8:) and near-infrared (L1) spectral types, is an as-yet
unresolved stellar/brown dwarf binary with late-type M dwarf and T dwarf
components. This conclusion is based on low-resolution, near-infrared
spectroscopy that reveals a subtle but distinctive absorption feature at 1.6
micron. The feature, which is also present in the combined light spectrum of
the M8.5 + T6 binary SCR 1845-6357, arises from the combination of FeH
absorption from an M8.5 primary and pseudo-continuum flux from a T5+/-1
secondary, as ascertained from binary spectral templates constructed from
empirical data. The binary templates provide a far superior match to the
overall near-infrared spectral energy distribution of 2MASS J0320-0446 than any
single comparison spectra. Laser guide star adaptive optics (LGS AO) imaging
observations, including the first application of LGS AO aperture mask
interferometry, fail to resolve a faint companion, restricting the projected
separation of the system to less than 8.3 AU at the time of observation. 2MASS
J0320-0446 is the second very low mass binary to be identified from unresolved,
low-resolution, near-infrared spectroscopy, a technique that complements
traditional high resolution imaging and spectroscopic methods.
