Dr. Christian REIMERS

Institute for Astronomy 
University Vienna 
Türkenschanzstr. 17 
A-1180 Wien, Austria 
Phone: +43 (1) 4277 518 31 
e-mail: reimers@astro.univie.ac.at 


Current fields of research:


Topic of PhD Thesis:

"Mass Loss by Inhomogeneous AGB-Winds - Detailed Structures in Planetary Nebulae"

AGB (Asymptotic Giant Branch) stars generate a massive dust driven stellar wind at the end of their lives. Ideally, this mass loss is spherical if the physical conditions are homogeneous at the stellar surface (e.g. temperature) and the stellar vicinity (e.g. density). Indeed, several physical processes induce deviations from these ideal conditions. This will affect the condensation of dust and therefore the mass loss rate. Inhomogeneities can also caused by cool spots at the stellar surface. These inhomogeneities of the temperature are able to emanate from a magnetic field or a huge convection cell within the stellar envelope. Both options are possible at the surface of AGB-stars. This thesis introduces a model for the investigation of the mass loss above cool spots. For that purpose a radiation hydrodynamic simulation (including a gas, a dust and a radiation component) has been used and modified for the special purposes of this problem. A flux tube geometry has been chosen which could have been produced by a magnetic field in the lower stellar atmosphere. Finally, a discussion has been carried out about the creation of dense knots in planetary nebula as a result of cool regions at the stellar surface. The result supports the theory that stellar spots generate significant inhomogeneities of the mass loss. But the formation of dense knots in planetary nebulae (e.g. in Helix Nebula or Escimo Nebula) have to be interpreted as a combination of inhomogeneities in the mass loss together with hydrodynamical instabilities. The model investigated describes the formation of initial inhomogeneities which can be later amplified by an interaction of the slow AGB wind with the fast tenuous wind of the hot central star of the planetary nebula. View the "trumpet star" .
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Topic of Master Thesis:

"Formung Planetarischer Nebel durch staubgetriebene AGB-Winde"
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Publications and Talks:

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