The same, but different: Stochasticity in binary destruction

TL;DR

This study uses N-body simulations to show that the destruction of intermediate binaries in star clusters is highly stochastic, leading to significant differences in binary populations even from identical initial conditions.

Contribution

It demonstrates the stochastic nature of binary destruction in clusters and how initial similarities can lead to diverse observed populations.

Findings

Binary destruction varies by a factor of >2 after 1 Myr.

Separation distributions can differ significantly in similar initial conditions.

Mass ratio distributions are less affected than binary fractions or separations.

Abstract

Observations of binaries in clusters tend to be of visual binaries with separations of 10s - 100s au. Such binaries are 'intermediates' and their destruction or survival depends on the exact details of their individual dynamical history. We investigate the stochasticity of the destruction of such binaries and the differences between the initial and processed populations using N-body simulations. We concentrate on Orion Nebula Cluster-like clusters, where the observed binary separation distribution ranges from 62 - 620 au. We find that, starting from the same initial binary population in statistically identical clusters, the number of intermediate binaries that are destroyed after 1 Myr can vary by a factor of >2, and that the resulting separation distributions can be statistically completely different in initially substructured clusters. We also find that the mass ratio distributions are altered (destroying more low mass ratio systems), but not as significantly as the binary fractions or separation distributions. We conclude that finding very different intermediate (visual) binary populations in different clusters does not provide conclusive evidence that the initial populations were different.