We present Keck II laser guide star adaptive optics observations of the brown dwarf WISEP J061135.13–041024.0 showing it is a binary with a component separation of 04. This system is one of the six known resolved binaries in which the magnitude differences between the components show a reversal in sign between the Y/J band and the H/K bands. Deconvolution of the composite spectrum results in a best-fit binary solution with L9 and T1.5 components. We also present a preliminary parallax placing the system at a distance of 21.2 ± 1.3?pc. Using the distance and resolved magnitudes we are able to place WISEP J061135.13–041024.0 AB on a color-absolute magnitude diagram, showing that this system contributes to the well-known "J-band bump" and the components' properties appear similar to other late-type L and early-type T dwarfs. Fitting our data to a set of cloudy atmosphere models suggests the system has an age 1?Gyr with WISE 0611–0410 A having an effective temperature (T eff) of 1275-1325?K and mass of 64-65 M Jup, and WISE 0611–0410 B having T eff?= 1075-1115?K and mass 40-65 M Jup.
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