High Precision Dynamical Masses for BrownDwarf Binaries

摘要

We present new dynamical mass estimates for a sample of brown dwarf binaries withsufficient precision (< 10%) to distinguish between current theoretical evolutionary models. Thissurvey, which has targeted 20 sources between spectral types M8 and T5, is enabled by the adventof laser guide star adaptive optics (LGS AO) on the Keck 11 10 m telescope. The LGS AO systemallows for both high precision (Epos < 1 mas) astrometry and spatially resolved, high-resolutionspectroscopy (δry < 1 km/s). A striking result from this work thus far is that for two systemswith precisely determined dynamical masses and similar spectral types, both evolutionary modelsconsidered correctly predict the mass in one case but underpredict the mass by several sigma in theother case. We postulate that this discrepancy may either stem from a disjoint between evolutionaryand atmospheric models at the M/L transition due to atmospheric dust treatment or potentially frommagnetic activity inhibiting convection.