The Low-mass Members of the Ursa Major Association

We present a set of over-densities in spatial-kinematic space previously identified by Kounkel & Covey (2019) that may constitute extended tidal tails associated with the nearby, 400 Myr old Ursa Major association. This sample of 1599 stars has a main-sequence turnoff point consistent with the age of Ursa Major, and might contain its missing low-mass members. It includes four candidate white dwarfs with properties that seem consistent with a total age of about 400 Myr, but we estimate from older white dwarf interlopers that about 33% of the sample may be contaminated by random field stars.