Use of the highly sensitive Hokupa ’ a curvature wavefront sensor has allowed for the first time direct adaptive optics ( AO ) guiding on brown dwarfs and VLM stars ( SpT = M 7 - L 2 ) .
An initial survey of 9 such objects discovered one 0.15 \arcsec binary ( 2MASSJ 1426316+155701 ) .
The companion is about half as bright as the primary ( \Delta K = 0.61 \pm 0.05 , \Delta H = 0.70 \pm 0.05 ) and has even redder colors H - K = 0.59 \pm 0.14 than the primary .
The blended spectrum of the binary has been previously determined to be M9.0 .
We modeled a blend of an M8.5 template and a L1-L3 template reproducing a M9.0 spectrum in the case of \Delta K = 0.61 \pm 0.05 , \Delta H = 0.70 \pm 0.05 .
These spectral types also match the observed H-K colors of each star .
Based the previously observed low space motion and H _ { \alpha } activity we assign an age of 0.8 ^ { +6.7 } _ { -0.3 } Gyr .
Utilizing this age range and the latest DUSTY models of the Lyon group we assign a photometric distance of 18.8 ^ { +1.44 } _ { -1.02 } pc and masses of M _ { A } = 0.074 ^ { +0.005 } _ { -0.011 } M _ { \odot } and M _ { B } = 0.066 ^ { +0.006 } _ { -0.015 } M _ { \odot } .
We therefore estimate a system separation of 2.92 _ { +0.22 } ^ { -0.16 } AU and a period of 13.3 _ { +3.18 } ^ { -1.51 } yr respectively .
Hence , 2M1426 is among the smallest separation brown dwarf binaries resolved to date .