Adaptive Optics imaging of VHS 1256-1257: A Low Mass Companion to a Brown Dwarf Binary System

Abstract

Recently, Gauza et al. (2015) reported the discovery of a companion to the late M-dwarf, VHS J125601.92-125723.9 (VHS 1256-1257). The companion's absolute photometry suggests its mass and atmosphere are similar to the HR 8799 planets. However, as a wide companion to a late-type star, it is more accessible to spectroscopic characterization. We discovered that the primary of this system is an equal-magnitude binary. For an age $\sim 300$ Myr the A and B components each have a mass of $64.6_{-2.0}^{+0.8}{M}_{\mathrm{Jup}}$, and the b component has a mass of $11.2_{-1.8}^{+9.7}$, making VHS 1256-1257 only the third brown dwarf triple system. There exists some tension between the spectrophotometric distance of $17.2\pm 2.6$ pc and the parallax distance of $12.7\pm 1.0$ pc. At 12.7 pc VHS1256-1257 A and B would be the faintest known M7.5 objects, and are even faint outliers among M8 types. If the larger spectrophotmetric distance is more accurate than the parallax, then the mass of each component increases. In particular, the mass of the b component increases well above the deuterium burning limit to $\sim 35M_{\mathrm{Jup}}$ and the mass of each binary component increases to $73_{-17}^{+20}{M}_{\mathrm{Jup}}$. At 17.1 pc, the UVW kinematics of the system are consistent with membership in the AB~Dor moving group. The architecture of the system resembles a hierarchical stellar multiple suggesting it formed via an extension of the star-formation process to low masses. Continued astrometric monitoring will resolve this distance uncertainty and will provide dynamical masses for a new benchmark system.

Accepted to ApJL

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Cited by in corpus (40)

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• MagAO: Status and Science
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• The Occurrence Rate of Quiescent Radio Emission for Ultracool Dwarfs using a Generalized Semi-Analytical Bayesian Framework
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• Polarimetric Detection of Exoplanets Transiting T- and L- Brown Dwarfs
• Detection of photometric variability in the very low-mass binary VHS J1256-1257AB using TESS and Spitzer
• Confirming the least massive members of the Pleiades star cluster
• Large Scale Searches for Brown Dwarfs and Free-Floating Planets
• Distinct Rotational Evolution of Giant Planets and Brown Dwarf Companions
• VLT/SPHERE survey for exoplanets around young, early-type stars including systems with multi-belt architectures
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• Next-generation Exo-REM atmospheric models: application to VHS 1256 b to emulate patchy clouds