The Low-Mass Members of the Ursa Major Association

TL;DR

This paper identifies potential extended tidal tails and low-mass members of the 400-million-year-old Ursa Major association using spatial-kinematic over-densities, highlighting candidate white dwarfs and contamination issues.

Contribution

It presents a new set of spatial-kinematic over-densities as potential tidal tails and low-mass members of Ursa Major, including candidate white dwarfs and contamination analysis.

Findings

Identification of 5 over-densities linked to Ursa Major

Candidate white dwarfs consistent with 400 Myr age

Estimated 33% contamination by field stars

Abstract

We present a set of 5 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 have a main-sequence turnoff point consistent with the age of Ursa Major, and might contain its missing low-mass members. It includes 4 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.