Disrupted Wide Binaries as Dynamical Probes of Galactic Structure

Abstract Many of the stars in the Galaxy are members of binary systems, the widest of which can eventually become disrupted due to a combination of kicks from passing objects 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 nonaxisymmetric 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 nonaxisymmetric perturbations create local fluctuations in the distribution of disrupted binary separations. We simulate the evolution of wide binary systems embedded in a gravitational potential with a rotating galactic bar, 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.