Investigation of Mass Transfer in Symbiotic Stars

Symbiotic stars are a type of wide interacting binary system consisting of a cool giant star and a hot companion, typically a white dwarf. These systems are characterized by wide binary separation, a long orbital period, and a dense circumstellar medium produced by mass transfer from giant to companion. The rates and mechanisms that govern the mass transfer process within symbiotic stars are currently poorly understood. Improving our understanding of mass transfer in these systems is important in connecting them to stellar objects such as planetary nebulae and Type Ia supernovae and in determining the role that symbiotic stars play in the late stages of stellar evolution. Research suggests that the ideal method of investigating mass transfer in symbiotic stars is to directly image the cool giant in these systems with an optical interferometer. This work presents the initial results of an optical interferometry study using the Center for High Resolution Angular Astronomy (CHARA) Array for the purpose of imaging symbiotic stars. The techniques of model fitting and direct imaging were used to analyze interferometric observations of the cool giant in four symbiotic star systems, searching for the presence of a filled Roche lobe. Once the radial diameter of each system was known, the geometric configuration of each giant could be constrained and the Roche filling factor determined, providing valuable information about the mass-loss mechanism at work in each system.