Common envelope evolution and triple dynamics as potential pathways to form the inner white dwarf + brown dwarf binary of the triple star system Gaia 0007-1605

TL;DR

This paper explores formation scenarios for the Gaia 0007-1605 system, demonstrating that common envelope evolution and triple dynamics, including Kozai-Lidov oscillations, can explain its current configuration.

Contribution

It provides a detailed analysis of how common envelope evolution and triple star dynamics can lead to the formation of a white dwarf + brown dwarf binary in Gaia 0007-1605, expanding understanding of such systems.

Findings

Common envelope evolution can explain the system with standard energy parameters.

Triple dynamics, including Kozai-Lidov oscillations, may trigger tidal migration.

The system likely formed through a combination of common envelope evolution and triple dynamics.

Abstract

The recently discovered system Gaia 0007-1605 consisting of a white dwarf with a close brown dwarf companion and a distant white dwarf tertiary very much resembles the triple system containing the first transiting planet candidate around a white dwarf ever discovered: WD 1856+534. We have previously argued that the inner binary in WD 1856+534 most likely formed through common envelope evolution but triple star dynamics represent an alternative scenario. Here we analyze different formation scenarios for Gaia 0007-1605. We reconstructed the potential common envelope evolution of the system and find that assuming standard parameters for the energy budget provides a reasonable solution. In agreement with other close white dwarf + brown dwarf binaries, and in contrast to WD 1856+534, no energy sources other than orbital energy during common envelope evolution are required to understand the current configuration of the system. In addition, using analytical prescriptions for triple dynamics, we show that Von Zeipel-Lidov-Kozai oscillations might have trigger tidal migration due to high eccentricity incursions (e \gtrsim 0.997). We conclude that the inner binary in Gaia 0007-1605, as its sibling WD 1856+534, formed either through common envelope evolution, triple dynamics or a combination of both mechanisms.