Individual Dynamical Masses of DENIS J063001.4$-$184014AB Reveal A Likely Young Brown Dwarf Triple

TL;DR

This study precisely measures the masses of a binary system of very low-mass objects, revealing both are substellar and indicating the system is likely young with a possible unresolved binary companion.

Contribution

The paper presents the first dynamical mass measurements of the binary components of DENIS J063001.4$-$184014AB, showing both are substellar and suggesting the system's youth and potential triple nature.

Findings

Both components are in the substellar mass regime.

The system is likely young (~200 Myr).

The secondary may be an unresolved binary.

Abstract

The binary nature of the M8.5 dwarf DENIS J063001.4$-$184014AB (DE0630$-$18) was discovered with astrometric monitoring from the ground, which determined the unresolved photocentric orbit and the trigonometric parallax of the system. Here we present radial-velocity monitoring and resolved observations in the near-infrared with Keck aperture masking that allow us to measure the system's relative separation and brightness. By combining all available information, we determine the individual dynamical masses of the binary components to be $M_1 = 0.052^{+0.009}_{-0.008} M_\mathrm{Sun}$ and $M_2 = 0.052^{+0.005}_{-0.004} M_\mathrm{Sun}$, both firmly in the substellar regime. These masses are surprising given the object's M8.5 optical spectral type and equivalent absolute magnitude, and the significant difference in brightness between the components ($\Delta{K}$ = 1.74$\pm$0.06 mag). Our results suggest that DE0630$-$18 is a relatively young system ($\sim$200 Myr) with a secondary component that is itself a potentially unresolved binary.