A New Method of Determining the Characteristics of Evolved Binary Systems Revealed in the Observed Circumstellar Patterns: Application to AFGL 3068

The binary characteristics of asymptotic giant branch (AGB) stars are imprinted in the asymmetric patterns of their circumstellar envelopes. We develop a simple method for constraining the orbital parameters of such binary stars from the characteristics of a spiral-like pattern observed at large distances from the central stars. We place constraints on the properties of AFGL 3068 (i.e., the masses of binary components, the viewing inclination of the orbital plane, as well as the orbital period, velocity, and separation). In particular, the mass of the companion star of AFGL 3068 is estimated to be greater than 2.6 solar mass. This method is applicable to other AGB stars, providing a step toward understanding the role binary stars can play in explaining the diverse patterns in observed circumstellar envelopes.