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| Paper: |
Hot-Star Mass-Loss Mechanisms: Winds and Outbursts |
| Volume: |
425, Hot and Cool: Bridging Gaps in Massive Star Evolution |
| Page: |
199 |
| Authors: |
Owocki, S. |
| Abstract: |
Mass loss from hot, massive stars can occur both through steady winds of OB and WR phases, and through relatively brief eruptions during their Luminous Blue Variable (LBV) phase. This talk reviews how radiative momentum associated with the extreme luminosity of such stars is tapped to drive their mass loss. For OB stars, the steady outflows seem well described by the classical theory of Castor, Abbott, and Klein (CAK) for scattering of continuum radiation from a stellar core by line-transitions of metal ions in an otherwise optically thin wind. For WR stars, the winds themselves become optically thick, leading to ionization shifts and mass loss that can exceed the single scattering limit, with driving now arising from a complex combination of continuum and line opacity. In LBVs, the mass loss can be even more extreme, with the mechanical energy even becoming comparable to the radiative luminosity, for example in giant eruptions when the star’s luminosity can actually exceed the classical Eddington limit. A key theme of this review is to compare and contrast the nature of radiative driving in these various stages of massive-star evolution. |
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