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arXiv · 1309.1500

The Exemplar T8 Subdwarf Companion of Wolf 1130

Gregory N. Mace·J. Davy Kirkpatrick·Michael C. Cushing·Christopher R. Gelino·Ian S. McLean·Sarah E. Logsdon·Edward L. Wright·Michael F. Skrutskie·Charles A. Beichman·Peter R. Eisenhardt·Kristin R. Kulas
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Abstract

We have discovered a wide separation (188.5") T8 subdwarf companion to the sdM1.5+WD binary Wolf 1130. Companionship of WISE J200520.38+542433.9 is verified through common proper motion over a ~3 year baseline. Wolf 1130 is located 15.83 +/- 0.96 parsecs from the Sun, placing the brown dwarf at a projected separation of ~3000 AU. Near-infrared colors and medium resolution (R~2000-4000) spectroscopy establish the uniqueness of this system as a high-gravity, low-metallicity benchmark. Although there are a number of low-metallicity T dwarfs in the literature, WISE J200520.38+542433.9 has the most extreme inferred metallicity to date with [Fe/H] = -0.64 +/- 0.17 based on Wolf 1130. Model comparisons to this exemplar late-type subdwarf support it having an old age, a low metallicity, and a small radius. However, the spectroscopic peculiarities of WISE J200520.38+542433.9 underscore the importance of developing the low-metallicity parameter space of the most current atmospheric models.

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Gregory N. Mace, J. Davy Kirkpatrick, Michael C. Cushing, Christopher R. Gelino, Ian S. McLean, Sarah E. Logsdon, Edward L. Wright, Michael F. Skrutskie, Charles A. Beichman, Peter R. Eisenhardt, Kristin R. Kulas. 2013-09-05. The Exemplar T8 Subdwarf Companion of Wolf 1130. https://doi.org/10.1088/0004-637x%2F777%2F1%2F36

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