AGB spiral pattern as a probe for binary companion
It is only very recent that asymptotic giant branch (AGB) stars reveal the circumstellar spiral patterns with the advent of high resolution and high sensitivity observations. Such patterns can provide possible evidence for the existence of central binary stars embedded in outflowing circumstellar envelopes, which provides an important clue for the late stellar evolution as well as the onset of asymmetrical planetary nebulae. I will first review the theoretical prediction for the binary-induced spiral-shell patterns on the AGB circumstellar envelopes. I will describe the importance of obtaining gas kinematics with ALMA in constraining the characteristics of the unknown, conceivable central binary stars. Its synergy with the HST dust scattered light and the VLA low frequency lines will be discussed.