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The First ALLWISE Proper Motion Discovery: WISEA J070720.50+170532.7

By Edward L. Wright, J. Davy Kirkpatrick, Christopher R. Gelino, Sergio Fajardo-Acosta, Gregory Mace, Peter R. Eisenhardt, Daniel Stern, Ian S. McLean, M. F. Skrutskie, Apurva Oza, M. J. Nelson, Michael C. Cushing, I. Neill Reid, Michele Fumagalli and Adam J. Burgasser


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^(–1) and a parallax of ω = 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 4.36 × 10^(–11) radians. No clear evidence of H_2 collision-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^(–1) relative to the Sun. Given its apparent magnitude, the distance is about 39 ± 9 pc and the tangential velocity is probably ≈330 km s^(–1), but a more precise parallax is needed to be certain

Publisher: American Astronomical Society
Year: 2014
OAI identifier: oai:authors.library.caltech.edu:44311
Provided by: Caltech Authors

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