A T8.5 Brown Dwarf Member of the ξ Ursae Majoris System

March 2013 • 2013AJ....145...84W

Authors • Wright, Edward L. • Skrutskie, M. F. • Kirkpatrick, J. Davy • Gelino, Christopher R. • Griffith, Roger L. • Marsh, Kenneth A. • Jarrett, Tom • Nelson, M. J. • Borish, H. J. • Mace, Gregory • Mainzer, Amanda K. • Eisenhardt, Peter R. • McLean, Ian S. • Tobin, John J. • Cushing, Michael C.

Abstract • 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—ξ Ursae Majoris. The angular separation is 8.'5, and the projected physical separation is ≈4000 AU. The sub-solar metallicity and low chromospheric activity of ξ 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 14 and 38 M J for system ages of 2 and 8 Gyr, respectively.


IPAC Authors

Chris Gelino

Associate Scientist


Davy Kirkpatrick

Senior Scientist