Recent observations of strikingly well-defined spirals around
asymptotic giant branch (AGB) stars point to the importance
of the presence of binary companions to explain the
circumstellar properties of such evolved stars. Binary motion
introduces directional dependence of an AGB wind, creating
an elongated spiral pattern in the plane of the sky. I will show
the use of the elongated spiral pattern to constrain key binary
quantities (i.e., inclination of the orbital plane, orbital period,
companion mass, and binary mass ratio). To determine the
AGB component's mass, it is required to obtain the kinematic
information of the circumstellar pattern from a molecular line
observation with the high resolution and sensitivity of current
interferometers, e.g., ALMA, EVLA, and SMA.