The strength of smoothed particle hydrodynamics in modelling binary interactions

The common envelope interaction gives rise to the formation of close binaries comprising at least one evolved star, such as a white dwarf. The idea behind the common envelope interaction is attractively simple. However, hidden complexities hav prevented a full understanding of the interaction. Hydrodynamic simulations of this interaction have been pivotal in gaining an understanding of compact binary systems and phenomena that may result from them, such as novae and x-ray binaries. Unfortunately, notable disagreements still exist amongst simulations and between simulated parameters of post-common envelope binaries and observations, such as differing final separations. In this work, we perform common envelope simulations with a new smoothed particle hydrodynamics code, Phantom, which has never been trained on this problem before. The lack of a simulation domain boundary, along with excellent conservation of energy and angular momentum, allows us to track the interaction in its entirety. We start by reproducing the simulations of Passy et al. (2012) to calibrate the code. Phantom is then used to carry out preliminary simulations of the phases preceding the fast inspiral and its effects on later stages of the interaction. We also investigated how bound gas that falls back onto the binary after the inspiral phase, leading to a new interaction. Although some computational issues remain to be resolved, Phantom has thus far proved to be an excellent tool in the study of binary interactions.