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Session 34 - New Results on the Nature of Eta Carinae.
Oral session, Wednesday, January 07
Lincoln,
In this talk we address the issue of the origin of Eta Carinae's bipolar bubble. We focus on two variations of a hydrodynamic interacting wind mechanism for producing the bubbles.
Our first model for the formation of the Homunculus nebula is a variant of the popular interacting stellar winds scenario. This model assumes that we have a fast, spherically symmetric wind emanating from the central star at the onset of the 1840 eruption, interacting with a constant, low density pre-eruptive ambient medium. The bipolarity is caused by the presence of a dense and cold torus of material surrounding the star. The bipolar nebula sculpted by this dense torus expands almost ballistically, eventually dwarfing the circumstellar torus, which is entrained in the equatorial material and hardly visible. This model, still under investigation, appears to reproduce fairly well the observed shape and size of the nebula.
In our second model we use an aspherical fast wind expanding into a previously deposited isotropic slow wind. For this case we have completed a series of numerical experiments to test if and how aspherical fast winds effect wind blown bubble morphologies. These experiments explore a variety of models for the latitudinal variations of fast wind flow parameters. The simulations demonstrate that aspherical fast winds can produce strongly bipolar outflows similar to what is seen in the Homunculus of Eta Car.
