  CO(J = 2-1) and SiO(J = 5-4) emission has been observed from the molecular
envelope around the nearby S star pi Gru. The CO line profile differs from the
usual parabolic shape seen in uniformly expanding envelopes; it has a
Voigt-like profile and two horns. A model for line formation in the envelope
shows that a tilted, expanding disk reproduces the observations well. The star
also has a fast molecular wind, with a projected outflow speed of at least 70
and perhaps as high as 90 km/s. The fast wind is presumably ejected from the
poles of the disk. These observations show that the complex structure seen in
many planetary nebulae, including quadrupolar structure and fast winds, may
largely evolve from structure formed while the progenitor star is in the last
stages of evolution on the AGB.
