June
2026
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2026AJ....171..332U
Authors
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Uyama, Taichi
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Currie, Thayne
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Xuan, Jerry W.
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De Rosa, Robert
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Kuzuhara, Masayuki
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Chen, Minghan
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Squicciarini, Vito
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Beichman, Charles
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Brandt, Timothy D.
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Deo, Vincent
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Guyon, Olivier
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Hirano, Teruyuki
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Janson, Markus
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Liu, Michael C.
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Mawet, Dimitri
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Lozi, Julien
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Nugroho, Stevanus
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Tamura, Motohide
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Vievard, Sebastien
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Bovie, Danielle
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Hori, Yasunori
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Kawahara, Hajime
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Kotani, Takayuki
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Li, Yiting
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Wang, Jason
Abstract
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We present the discovery of a low-mass companion located at ρ ∼ 0 .″ 85 (rproj ≍ 62 au) from the early type 1.3 Gyr old star HIP 53005 using direct-imaging data from the Subaru and Keck Telescopes and astrometry from the Hipparcos─Gaia Catalog of Accelerations. The companion, HIP 53005 C, is a component of a multiple system also including a ≍ 12 .″ 4 separation M-dwarf companion inducing a negligible proper motion acceleration. HIP 53005 C's position on color─magnitude diagrams, the fit of its spectral energy distribution to atmosphere models, and its location on an empirical mass-magnitude diagram all suggest that it lies at the M/L transition and near the hydrogen-burning limit (∼80 MJup). However, our orbital fitting combining direct-imaging relative astrometry with proper motion acceleration favors a much higher dynamical mass of ∼185MJup. An additional unseen, more closely orbiting companion below the detection limit (at ρ≲0.″2 )) may explain this discrepancy. Alternatively, HIP 53005C could be a low-mass binary like Gliese 229Bab, making this system an intriguing laboratory for studying multiple star formation.
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