Stellar winds from hot low-mass stars
W.-R. Hamann
Stellar winds appear as a persistent feature of hot stars, irrespective
of their wide range of different luminosities, masses, and chemical
composition. Among the massive stars, the Wolf-Rayet types show
considerably stronger mass loss than the O stars. Among hot low-mass
stars, stellar winds are seen at central stars of planetary nebulae,
where again the hydrogen-deficient stars show much stronger winds than
those central stars with ``normal'' composition. We also studied
mass-loss from a few extreme helium stars and sdOs. Their mass-loss rate
roughly follows the same proportionality with luminosity to the power
1.5 as the massive O stars. This relation roughly marks a lower limit
for the mass loss from hot stars of all kinds, and provides evidence
that radiation pressure on spectral lines is the basic mechanism at
work. For certain classes of stars the mass-loss rates lie
significantly above this relation, for reasons that are not yet fully
understood. Mass-loss from low-mass stars may affect their evolution,
by reducing the envelope mass, and can easily prevent diffusion from
establishing atmospheric abundance patterns. In close binary systems,
their winds can feed the accretion onto a companion.
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