Edward L. Wright, M. F. Skrutskie, J. Davy Kirkpatrick, Christopher R. Gelino, Roger L. Griffith, Kenneth A. Marsh, Tom Jarrett, M. J. Nelson, H. J. Borish, Gregory Mace, Amanda K. Mainzer, Peter R. Eisenhardt, Ian S. McLean, John J. Tobin, Michael C. Cushing
The Wide-field Infrared Survey Explorer has revealed a T8.5 brown dwarf (WISE J111838.70+312537.9) that exhibits common proper motion with a solar-neighborhood (8 pc) quadruple star system - Xi Ursae Majoris. The angular separation is 8.5 arc-min, and the projected physical separation is about 4000 AU. The sub-solar metallicity and low chromospheric activity of Xi UMa A argue that the system has an age of at least 2 Gyr. The infrared luminosity and color of the brown dwarf suggests the mass of this companion ranges between 28 and 58 Jupiter masses for system ages of 2 and 8 Gyr respectively.
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http://arxiv.org/abs/1203.5764
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