A benchmark white dwarf-ultracool dwarf wide field binary
Abstract
We present the discovery and multiwavelength characterization of VVV J1438-6158 AB, a new field wide-binary system consisting of a $4.6^{+5.5}_{-2.4}~{\rm Gyr}$ and $T_{\rm eff} = 9500\pm 125~\mathrm{ K}$ DA white dwarf (WD) and a $T_{\rm eff} = 2400\pm 50~\mathrm{ K}$ M8 ultracool dwarf (UCD). The projected separation of the system is $a = 1236.73~{\rm au}$ ($\sim 13.8\, \mathrm{ arcsec}$), and although along the line of sight towards the Scorpius-Centaurus stellar association, VVV J1438-6158 AB is likely to be a field star, from a kinematic 6D probabilistic analysis. We estimated the physical and dynamical parameters of both components via interpolations with theoretical models and evolutionary tracks, which allowed us to retrieve a mass of $0.62\pm 0.18~\mathrm{ M}_\odot$ for the WD, and a mass of $98.5\pm 6.2~\mathrm{ M}_{\rm Jup}$ ($\sim 0.094\pm 0.006~\mathrm{ M}_\odot$) for the UCD. The radii of the two components were also estimated at $0.01309\pm 0.0003~\mathrm{ R}_{\odot }$ and $1.22\pm 0.05~\mathrm{ R}_{\rm Jup}$, respectively. VVV J1438-6158 AB stands out as a benchmark system for comprehending the evolution of WDs and low-mass companions given its status as one of the most widely separated WD+UCD systems known to date, which likely indicates that both components may have evolved independently of each other, and also being characterized by a large-mass ratio ($q = 0.15\pm 0.04$), which likely indicates a formation pathway similar to that of stellar binary systems.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2024
- DOI:
- 10.1093/mnras/stad3911
- arXiv:
- arXiv:2312.10158
- Bibcode:
- 2024MNRAS.52710737F
- Keywords:
-
- brown dwarfs;
- stars: binaries;
- evolution;
- white dwarfs;
- infrared: stars;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in MNRAS, 11 pages, 6 figures