2014AJ....147...61W

While quality checking a new motion-aware co-addition of all 12.5 months of Wide-field Infrared Survey Explorer (WISE) data, we found that the source WISE J070720.48+170533.0 moved 0.''9 in six months. Backtracking this motion allowed us to identify this source as 2MASS J07071961+1705464, with several entries in the USNO B catalog. An astrometric fit to these archival data gives a proper motion of µ = 1793±2 mas/yr and a parallax of {piv} = 35±42 mas. Photometry from WISE, 2MASS, and the POSS can be fit reasonably well by a blackbody with T = 3658 K and an angular radius of 4.36x10^–11 radians. No clear evidence of H₂collision-induced absorption is seen in the near-infrared. An optical spectrum shows broad deep CaH bands at 638 and 690 nm, broad deep Na D at 598.2 nm, and weak or absent TiO, indicating that this source is an ultra-subdwarf M star with a radial velocity v_rad~ -21±18 km/s relative to the Sun. Given its apparent magnitude, the distance is about 39±9 pc and the tangential velocity is probably ~330 km/s, but a more precise parallax is needed to be certain.