# Collisional N-Body Dynamics Coupled to Self-Gravitating Magnetohydrodynamics Reveals Dynamical Binary Formation

## TL;DR

This paper presents a comprehensive simulation model combining magnetohydrodynamics and stellar dynamics to study binary star formation in young clusters, revealing insights into binary fractions and cluster evolution.

## Contribution

The study introduces a novel integrated simulation approach coupling MHD with N-body dynamics to investigate binary formation during star cluster evolution.

## Key findings

- Simulations match observed binary fractions for massive stars.
- Binary fractions are lower than observed for low-mass stars.
- Binaries accumulate near the hard-soft boundary, influencing cluster contraction.

## Abstract

We describe a star cluster formation model that includes individual star formation from self-gravitating, magnetized gas, coupled to collisional stellar dynamics. The model uses the Astrophysical Multi-purpose Software Environment (AMUSE) to integrate an adaptive-mesh magnetohydrodynamics code (FLASH) with a fourth order Hermite N-body code (ph4), a stellar evolution code (SeBa), and a method for resolving binary evolution (multiples). This combination yields unique star formation simulations that allow us to study binaries formed dynamically from interactions with both other stars and dense, magnetized gas subject to stellar feedback during the birth and early evolution of stellar clusters. We find that for massive stars, our simulations are consistent with the observed dynamical binary fractions and mass ratios. However, our binary fraction drops well below observed values for lower mass stars, presumably due to unincluded binary formation during initial star formation. Further, we observe a build up of binaries near the hard-soft boundary that may be an important mechanism driving early cluster contraction.