Sculpting an AGB Mass-Loss Envelope into a Bipolar Planetary Nebula: High-Velocity Outflows in V Hydrae

Abstract

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.

33 pages, 6 figures

References in corpus (4)

• Preplanetary Nebulae: An HST Imaging Survey and a New Morphological Classification System
• Binarity in Cool Asymptotic Giant Branch Stars: A Galex Search for Ultraviolet Excesse
• Echelle long-slit optical spectroscopy of evolved stars
• PPN as Explosions: Bullets vs Jets and Nebular Shaping

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• The Rapidly Evolving AGB Star, V Hya: ALMA finds a Multi-Ring Circus with High-Velocity Outflows
• VLT observations of the asymmetric Etched Hourglass Nebula, MyCn 18
• High-Velocity Bullets from V Hydrae, an AGB Star in Transition: Ejection History and Spatio-Kinematic Modeling
• PACS and SPIRE range spectroscopy of cool, evolved stars
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• Warm CO in evolved stars from the THROES catalogue. II. Herschel/PACS spectroscopy of C-rich envelopes
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