Disrupted Wide Binaries as Dynamical Probes of Galactic Structure

Abstract

Many of the stars in the Galaxy were formed in binary systems. The widest of these can eventually become disrupted due to a combination of kicks from passing stars and the Galactic tidal field. If the Galactic disk were purely axisymmetric, the stars from a disrupted binary system would slowly drift apart on nearly identical orbits. We study how the existence of non-axisymmetric structures, such as a rigidly rotating bar, can greatly alter this picture. In particular, we show how the orbital dynamics near the resonances sourced by these perturbations can create local fluctuations in the distribution of disrupted binary separations. We simulate the evolution of wide binary systems embedded in gravitational potentials with rotating galactic bars, and show how features and fluctuations in the distribution of disrupted binaries can be used to locate bar resonances and constrain the bar's pattern speed and amplitude.