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Paper: Is the Outflow from RT Vir Bipolar or Rotating?
Volume: 199, Asymmetrical Planetary Nebulae II: From Origins to Microstructures
Page: 79
Authors: Yates, J. A.; Richards, A. M. S.; Gledhill, T. M.; Bains, I.
Abstract: We present high angular resolution observations of H2O maser proper motions in the circumstellar envelope of the semi-regular variable RT Vir. These MERLIN observations, at 12-mas angular resolution, were used to map H2O maser emission at ~2 week intervals over 10 weeks in 1996, during which period the brightness distribution changed markedly. The emission covers a region > 100 mas in radius on the sky. It is faintest along an NNE-SSW axis. The average cloud size is 10 mas (1.4 au), and the inferred density contrast between the clouds and the ambient medium is 30:1. The proper motions of 18 maser clouds were measured with > 2σ significance; 11 were identified at all epochs. At the Hipparcos distance of 140 pc these yielded an average expansion velocity of 12 km/s. The motions show strong radial expansion and the limit on any rotational component is < 0.2 km/s. Hence up to 14 au from the star the envelope has negligible rotation.
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