Discovery of a resolved white dwarf-brown dwarf binary with a small projected separation: SDSS J222551.65+001637.7AB
Abstract
We present the confirmation of SDSS J222551.65+001637.7AB as a closely separated, resolved, white dwarf-brown dwarf binary. We have obtained spectroscopy from GNIRS and seeing-limited Ks-band imaging from NIRI on Gemini North. The target is spatially resolved into its constituent components: a 10926 ± 246 K white dwarf, with log g = 8.214 ± 0.168 and a mass of 0.66$^{+0.11}_{-0.06}$ M⊙, and an L4 brown dwarf companion, which are separated by 0.9498 ± 0.0022 arcsec. We derive the fundamental properties of the companion from the Sonora-Bobcat evolutionary models, finding a mass of 25-53 MJup and a radius of 0.101-0.128 R⊙ for the brown dwarf, at a confidence level of 1σ. We use WDWARFDATE to determine the age of the binary as $1.97^{+4.41}_{-0.76}$ Gyr. A kinematic analysis shows that this binary is likely a member of the thick disc. The distance to the binary is 218$^{+14}_{-13}$ pc, and hence the projected separation of the binary is 207$^{+13}_{-12}$ au. Whilst the white dwarf progenitor was on the main sequence the binary separation would have been 69 ± 5 au. SDSS J222551.65+001637.7AB is the third closest spatially resolved white dwarf-brown dwarf binary after GD 165AB and PHL 5038AB.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 2023
- DOI:
- 10.1093/mnras/stac3807
- arXiv:
- arXiv:2301.02101
- Bibcode:
- 2023MNRAS.519.5008F
- Keywords:
-
- brown dwarfs;
- white dwarfs;
- binaries;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 9 pages, 6 figures. Accepted for publication in MNRAS