Wide Binaries as Dynamical Probes of the Milky Way’s Structure

A large fraction of the stars in the Milky Way were born in binary systems. Over time, the two stars in each system are slowly driven apart from each other, primarily due to perturbations from other passing stars, and eventually some of the systems become unbound because of the galactic tidal field. From this point on, the two stars can essentially be thought of as two test particles with nearly identical orbital parameters and phases, that slowly drift apart from each other due to the small difference in their orbital frequencies. As a result, they can serve as excellent probes of the underlying galactic potential, much like the tidally disrupted remnants of globular clusters known as stellar streams. Yet unlike stellar streams, the remnants of disrupted binary systems are distributed throughout the galactic disc, and can therefore shed light on its entire phase space. In this talk, I will describe how the distribution of tidally disrupted wide binary systems throughout the galactic disc can be used to study non-axisymmetric perturbations of the MW’s gravitational potential. The dynamical evolution of the two stars from a recently disrupted binary system can change dramatically in the vicinity of resonant regions in the disc, such as those driven by the Milky Way’s rotating bar. I will demonstrate how this effect leads to unique signatures that depend on the evolution of the bar’s amplitude and pattern speed, and discuss how these signatures may be detectable in the Gaia two-point correlation function. Finally, I will describe how tidally disrupted open clusters are also susceptible to the same effect, and may create even stronger signals in the Gaia data.