Previous abstract Next abstract

Session 50 - Disks and Bipolar Outflows from Hot Stars - I.
Oral session, Wednesday, June 12
Union Theater,

[50.03] Observations of discs in hot stars

L. B. F. M. Waters (U. Amsterdam and SRON Lab. for Space Res. Groningen)

Outflows from hot stars often show strong deviations from spherical symmetry. Radiation driven winds are inherently unstable and inhomogeneities can rapidly grow. Rotation also plays an important role in driving the geometry of hot star winds. The class of rapidly rotating Be stars is a beautiful example of the very flattened geometry that can result from the interplay between rotation and radiation forces in the outflows of hot stars. Recent theoretical developments for the first time show how rapid rotation can result in a disc-like geometry in hot star winds. The Be phenomenon however is strongly time variable, an aspect that has yet to be explained. Apart from Be stars, the B[e] supergiants also show strong evidence for disc-like outflows, and may be the more luminous counterpart of the main sequence Be stars. Their evolutionary status and nature are less well understood however.

This talk will address the structure of discs in Be and B[e] stars and its time variability. Key questions that will be considered are: (i) are Be star discs be 'fed' by the polar wind only, or is additional mass loss required? What could be the origin of this additional mass loss? (ii) what determines the structure of Be star discs? (iii) Why are Be star discs variable?

Program listing for Wednesday