Sculpting an AGB Mass-Loss Envelope into a Bipolar Planetary Nebula:
  High-Velocity Outflows in V Hydrae
  We have carried out high-resolution spectroscopic observations of the carbon
star V Hya, covering the 4.6 micron band of CO. These data, taken over 7
epochs, show that the circumstellar environment of V Hya consists of a complex
high-velocity (HV) outflow containing at least six kinematic components with
expansion velocities ranging between 70 and 120 km/s, together with a
slow-moving normal outflow at about 10 km/s. Physical changes occur in the HV
outflow regions on a time-scale as short as two days, limiting their extent to
< ~ 10^{16} cm. The intrinsic line-width for each HV component is quite large
(6-8 km/s) compared to the typical values (~1 km/s) appropriate for normal AGB
circumstellar envelopes (CSEs), due to excess turbulence and/or large velocity
gradients resulting from the energetic interaction of the HV outflow with the V
Hya CSE. We have modelled the absorption features to set constraints on the
temperature distribution in, and the mass ejection-rates for gas in the main HV
components.
