Gasdynamical Simulations of the Large and Little Homunculus Nebulae of Carinae

We here present two-dimensional, time-dependent radiatively coolinghydrodynamical simulations of the large and little Homunculus nebulae around$\eta$ Carinae. We employ an alternative scenario to previous interactingstellar wind models which is supported by both theoretical and observationalevidence, where a non-spherical outburst wind (with a latitudinal velocitydependence that matches the observations of the large Homunculus), which isexpelled for 20 years, interacts with a pre-eruptive slow wind also with atoroidal density distribution, but with a much smaller equator-to-polar densitycontrast than that assumed in previous models. A second eruptive wind withspherical shape is ejected about 50 years after the first outburst, and causesthe development of the little internal nebula. We find that, as a result of anappropriate combination of the parameters that control the degree of asymmetryof the interacting winds, we are able to produce not only the structure andkinematics of both Homunculus, but also the high-velocity equatorial ejecta.These arise from the impact between the non-spherical outburst and thepre-outburst winds in the equatorial plane.Comment: ApJ Lett. in pres