Numerical simulations of the great eruption of eta Carinae from the 1840s I. Revisiting the explosion scenario

In this work, we present new 2D hydrodynamical simulations of the major eruption of eta Car in the 1840s, which resulted in the formation of a bipolar nebula that is commonly known as the large Homunculus. In our numerical models, we have included the high-speed component of 10 000 km s(-1), which was detected in recent observations, providing direct evidence of an explosive event. Here, we investigate whether such a violent explosion is able to explain both the shape and the dynamical evolution of eta Car's nebula. As in our previous work, we have assumed a two-stage scenario for eta Car's eruption: a slow outflow phase for a few decades before the eruption, followed by the explosive event. From the collision of these outflow phases, the large Homunculus is produced. Our numerical simulations show that such a scenario does not resemble some of the observed physical features and the expansion of the nebula. Notwithstanding, we also explore other injection parameters (mass-loss rate and ejection velocity) for these outflow phases. In particular, we find that an explosion with an intermediate speed of 1000 km s(-1) is able to reproduce the morphology and the kinematical age of the large Homunculus.