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 4.6μm band of CO. These data, taken over 7 epochs, show that the circumstellar environment of V Hya consists of a complex highvelocity (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 be . 10 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. Subject headings: stars: AGB and post-AGB, stars: mass-loss, stars: carbon, ISM: jets and outflows, stars: individual (V Hydrae)