Another result from the WISE mission: A T8.5 Brown Dwarf Member of the Xi Ursae Majoris System
WISE J111838.70+312537.9 has common proper motion with the Xi Ursae Majoris system.
The representation of the system in nearstars.stc might need an update: I'm not sure that the star we've got as "? UMa C" is actually a confirmed member of the system. From what I can tell it is more likely that ? UMa Bb is a star (probably M or K type) in a nearly face-on orbit rather than a brown dwarf, which I believe is ruled out by the implied total mass of the system.