Mass transfer dynamics in double degenerate binary systems

TL;DR

This study uses numerical simulations to analyze the mass transfer process in double white dwarf systems before merger, highlighting the importance of initial conditions and demonstrating convergence across different computational methods.

Contribution

It reveals that the duration of mass transfer in double white dwarf systems is highly sensitive to initial conditions and shows that different simulation methods can produce consistent results with proper setup.

Findings

Mass transfer can last for many orbital periods with proper initial conditions.

Results are resolution-biased, providing lower limits to real systems.

Different numerical methods converge to similar outcomes when carefully prepared.

Abstract

We present a numerical study of the mass transfer dynamics prior to the gravitational wave-driven merger of a double white dwarf system. Recently, there has been some discussion about the dynamics of these last stages, different methods seemed to provide qualitatively different results. While earlier SPH simulations indicated a very quick disruption of the binary on roughly the orbital time scale, more recent grid-based calculations find long-lived mass transfer for many orbital periods. Here we demonstrate how sensitive the dynamics of this last stage is to the exact initial conditions. We show that, after a careful preparation of the initial conditions, the reportedly short-lived systems undergo mass transfer for many dozens of orbits. The reported numbers of orbits are resolution-biased and therefore represent only lower limits to what is realized in nature. Nevertheless, the study shows convincingly the convergence of different methods to very similar results.