Discovery of a Low-Mass Companion to the Accelerating Star HIP 53005 with Strongly Conflicting Mass Estimates

2026/04/04 by Taichi Uyama, Thayne Currie, Jerry W. Xuan +22 · 1 voice
Physics and Astronomy · #astro-ph.EP #astro-ph.GA #astro-ph.SR

paper · pdf · doi:10.3847/1538-3881/ae5c06

Abstract

We present the discovery of a low-mass companion located at ρ ∼ 0\farcs85 (r_{\rm proj} ≈ 62~au) from the early-type 1.2 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\farcs4-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~M_{\rm Jup}). However, our orbital fitting combining direct-imaging relative astrometry with proper motion acceleration favors a much higher dynamical mass of ∼185 M_{\rm Jup}. An additional unseen, more closely-orbiting companion below the detection limit (at ρ\lesssim0\farcs2)) 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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Discussions

• Accelerating star surveys with SCExAO strike again! This time a work led by Uyama-san identifying a potential GJ229B-like companion (or something else strange going on) arxiv.org/abs/2604.03767 [bsky, 0 points, 0 comments]

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