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School of Phyics
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Tim Harries
Bipolar nebulae formation
Introduction
Bipolar planetary nebulae are some of the most beautiful
objects in our Galaxy. The collimation mechanism for the nebulae
appears to be an equatorial high-density belt of dust and gas, which
acts like a jet nozzle on a fast stellar wind. Although hydrodynamical
models based on this "interacting winds theory" are capable of
reproducing most of the observed nebula morphologies, the origin of
the collimating material is poorly understood, and observational
evidence is sparse.
The origin of the equatorial collimator
We are developing the observational technqiues and modelling codes
required to provide evidence for equatorially enhanced mass-loss
around AGB and post-AGB stars. Scattering of starlight by an
equatorial disk or torus of dust will result in linear polarization,
and we have obtained an extensive database of spectropolarimetry of
red giants, ABG stars, post-AGB stars and proto-planetary nebulae in
order to search for this polarization signal. We are also using
Raman-scattering in symbiotic
binaries to measure the geometry of the stellar winds of Mira
stars.
See also Tim
Harries' publication list and the Group publications
list .
Up to Astrophysics research at Exeter.