Close binary STARS with periods less than roughly 100 days produce a wide variety of astrophysical phenomena, and yet their origins remain unknown. Theoretical models suggest that binaries and…

The National Aeronautics and Space Administration (NASA) awarded a $495,204.93 grant to the University of Arizona, doing business as the Arizona Board of Regents, to conduct research on the origins and evolution of close binary star systems. The research will involve a two-pronged approach, including high-resolution 3D hydrodynamic numerical experiments to model the interactions of binary stars with their natal disks, as well as the construction of mock populations of close binaries and triple star systems to study the impact of various mechanisms on the final statistics of these systems. This work is expected to both leverage and provide predictions for data from the Gaia space observatory. The grant does not have a set-aside designation.

Close binary STARS with periods less than roughly 100 days produce a wide variety of astrophysical phenomena, and yet their origins remain unknown. Theoretical models suggest that binaries and higher order multiples begin their lives at separations of 10S-1000S of AU. Some fraction of these then shed energy and angular momentum via a range of processes to arrive on short orbits where they interact, explode, and provide for precise measurements of stellar parameters. Their proposal takes a two pronged approach to constraining the origin and evolution of close binaries: they will carry out a series of high resolution 3D hydrodynamic numerical experiments in order to place tight constraints on how orbits evolve when binaries interact with their natal disks. They consider the interactions of STARS with individual circumstellar disks as well as the interaction of binaries embedded within a single disk. In conjunction with their modeling of these detailed physical processes, they will construct mock populations of close binaries and triple star systems beginning from realistic initial conditions for formation. They will combine parameterized models for early phase orbit migration in disks, dynamical instabilities in multi-star systems, and the direct integration of secular evolution equations. Their secular evolution models will also include general relativistic effects, tidal precession and tidal dissipation. They will vary our initial conditions in order to produce a range of mock populations, which will allow them to calculate how various combinations of initial distributions and mechanisms shape the final statistics of binary and triple systems. Their modeling approach will focus on two novel aspects of triple star statistics: mass ratio distributions and relative inclinations. Their work will be well timed to both utilize and make predictions for gaia, which will increase the sample of well characterized triple star systems by two orders of magnitude. We demonstrate how their models will interact with these new data sets.