Gasdynamical Simulations of the Large and Little Homunculus Nebulae of Carinae

Abstract

Here we present two-dimensional, time-dependent radiatively coolinghydrodynamical simulations of the large and little Homunculus nebulaearound h Carinae. We employ an alternative scenario to previousinteracting stellar wind models that is supported by both theoreticaland observational evidence, where a nonspherical outburst wind (with alatitudinal velocity dependence that matches the observations of thelarge Homunculus), which is expelled for 20 years, interacts with apreeruptive slow wind also with a toroidal density distribution but witha much smaller equator-to-polar density contrast than that assumed inprevious models. A second eruptive wind with spherical shape is ejectedabout 50 years after the first outburst and causes the development ofthe little internal nebula. We find that as a result of an appropriatecombination of the parameters that control the degree of asymmetry ofthe interacting winds, we are able to produce not only the structure andkinematics of both Homunculus but also the high-velocity equatorialejecta. These arise from the impact between the nonspherical outburstand the preoutburst winds in the equatorial plane.