  Close interactions and mass transfer in binary stars can lead to the
formation of many different exotic stellar populations, but detailed modeling
of mass transfer is a computationally challenging problem. Here, we present an
alternate Smoothed Particle Hydrodynamics approach to the modeling of mass
transfer in binary systems that allows a better resolution of the flow of
matter between main-sequence stars. Our approach consists of modeling only the
outermost layers of the stars using appropriate boundary conditions and ghost
particles. We arbitrarily set the radius of the boundary and find that our
boundary treatment behaves physically and conserves energy well. In particular,
when used with our binary relaxation procedure, our treatment of boundary
conditions is also shown to evolve circular binaries properly for many orbits.
The results of our first simulation of mass transfer are also discussed and
used to assess the strengths and limitations of our method. We conclude that it
is well suited for the modeling of interacting binary stars. The method
presented here represents a convenient alternative to previous hydrodynamical
techniques aimed at modeling mass transfer in binary systems since it can be
used to model both the donor and the accretor while maintaining the density
profiles taken from realistic stellar models.
