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″. 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.

Disk or Companion: Characterizing Excess Infrared Flux in Seven White Dwarf Systems with Near-infrared Spectroscopy

“…If the brown dwarf was more widely separated from the white dwarf progenitor, they would have evolved like two single stars. There are about a dozen wide white dwarf-brown dwarf pairs, which were detected via direct imaging (e.g., Becklin & Zuckerman 1988;French et al 2023). Sometimes, the evolution path is less clear, as in the case of the recent discovery of Gaia 0007-1605, an old hierarchical triple system with an inner white dwarf-brown dwarf binary and an outer white dwarf system (Rebassa-…”

The Large Array Survey Telescope—Science Goals

“…They provide insights to many aspects of binary evolution, such as the impact of increased stellar rotation on flare rates, disk disruption, tidal effects, angular momentum exchange (Morgan et al 2016), age determination of field M-dwarfs, and chromospheric activity-age relation calibration (Silvestri et al 2005). The latter are candidates for cataclysmic variables (CVs) with sub-stellar donors, of which only ∼10 are currently known (e.g., French et al 2023). These systems are useful laboratories for studying the transition from a post common-envelope binary to a pre-CV (e.g., Longstaff et al 2019).…”

A sample of 554 white dwarfs showing infrared excess from Gaia EDR3 and CatWISE catalogs

“…Wide resolved binaries are unlikely to suffer effects from the companion during their evolution and will have evolved as single stars. In the case of close systems, the common envelope stage may have disturbed the evolution of each component (French et al 2023).…”