Tidal disruptions of close white dwarf binaries by intermediate mass black holes

TL;DR

This study uses numerical simulations to analyze how close white dwarf binaries are tidally disrupted by intermediate mass black holes, revealing dependencies on binary configuration and mass differences.

Contribution

It provides detailed insights into the outcomes of tidal disruptions of white dwarf binaries by intermediate mass black holes, highlighting the effects of binary configuration and mass asymmetry.

Findings

Outcome depends on binary positional configuration at pericenter.

Distinct behaviors observed for non-identical mass binaries.

Prograde and retrograde binary motions produce different observable signatures.

Abstract

We perform a suite of numerical simulations of tidal disruption events, using smoothed particle hydrodynamics, for a close binary system consisting of two low-mass white dwarfs, and an intermediate mass non-spinning black hole. The binary components are considered to be detached and on the same plane with the black hole. Our results quantify how the outcomes of these events depend crucially on the positional configuration of the binary components at the orbital pericenter, and we also show how distinctive behaviour for non-identical mass binaries arise, as compared to identical ones. We highlight these differences on observables such as mass fallback rates, kick velocities and gravitational waves, and also compute clump formation time within the stellar debris. In our setup, prograde binary motion, where the angular momentum of the binary is in the same direction as that of the center of mass motion around the black hole, is qualitatively similar to multiple events of single star tidal disruptions. However, we argue that interactions between stellar debris in the corresponding retrograde scenarios result in different and distinct outcomes. Our results should serve as indicative benchmarks in the observational aspects of tidal interactions between close white dwarf binaries and intermediate mass black holes.