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Session 26 - Proto Stars to Supernovae.
Oral session, Monday, June 08

[26.03] Line-Driven Ablation and Wind Tilting by External Irradiation

K. Gayley (University of Iowa), S. Owocki (Bartol Research Inst.), S. Cranmer (Harvard Smithsonian)

Sobolev opacity in a hot-star wind preferentially scatters photons that are incident along the direction of steepest velocity gradient. This non-isotropic response can rotate the force vector relative to the direction of net radiative flux, in a manner analogous to the way a non-isotropic sail and keel can allow a boat to sail upwind. For hot star binaries, the curious feedback between the radiative forces and the flows they drive allows for counter-intuitive self-consistent solutions. For example, we show that illumination that is purely external to a reflecting radiative-equilibrium atmosphere can ablate a highly tilted and fast wind, loosely reminiscent of ``tacking'' in the sailing analogy. The conclusion is that whenever the radiation source geometry is complicated, the non-isotropic nature of Sobolev opacity must be carefully accounted for to obtain even a qualitative understanding of the atmospheric response. Thus CAK theory continues to reveal new surprises even in its most basic formulation.

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