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 \pm 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 .