Collaborative Research: Establishing the theoretical framework for eccentric interacting binaries

Mass transfer processes in binary systems in which the orbits have a high degree of mathematical eccentricity are central to many astrophysical phenomena. Examples range from stellar donors repeatedly disrupted by massive black holes as potential sources for repeated partial tidal disruption events (rpTDEs), to Jupiter-like planets in other solar systems whose fate during high-eccentricity migration depends on whether mass transfer occurs. Despite its importance, mass transfer in eccentric systems has been studied mainly through short-duration numerical simulations that cannot capture long-term orbital changes and whose results require caution when extrapolated. Until recently, theoretical models have been limited to hydrostatic, circular, spin-synchronized donors. A collaborative research team at universities in Montana, Virginia, and Texas will apply their newly developed nonlinear hydrodynamic model capable of studying general donors in arbitrarily eccentric orbits. In addition, the investigators will strengthen STEM education in rural Montana, mentor undergraduates through a summer program in Texas, and promote undergraduate research through the creation of Python notebooks which emphasize the basic skills in programming, math, physics, and astronomy required to begin research. The project will further develop the theoretical framework for eccentric interacting binaries. The models will describe how mass loss modifies the orbit and donor’s structure. Impacts of nonlinear dissipation will also be examined. The proposed theory of eccentric interacting binaries will provide a unifying framework that connects theoretical understanding with numerical simulations, enabling their validation, interpretation, and extrapolation. This synergy will lead to advances in a wide array of astrophysical phenomena, from identifying the sources of high-energy transients to constraining the formation pathways of exoplanetary systems. The new model may explain not only the physical origin of at least a subclass of rpTDEs but also offer a novel means of constraining the dynamical stellar environments of galactic nuclei. On the exoplanet side, it has the potential to account for both the observed efficiency of Hot Jupiter formation and the existence of Hot Neptunes (HN) within the nominal “HN desert.” This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.