Numerical simulations of the 1840s great eruption of $\eta$ Carinae: I. Revisiting the explosion scenario

TL;DR

This study uses two-dimensional hydrodynamical simulations to explore the 1840s eruption of $ta$ Carinae, testing explosion scenarios to explain the nebula's shape and dynamics, and finds an intermediate-speed explosion best matches observations.

Contribution

It introduces new hydrodynamical models incorporating recent high-speed observations and evaluates different eruption scenarios for $ta$ Carinae.

Findings

An explosion with 1000 km/s best reproduces the nebula's morphology.

High-speed components of 10000 km/s do not match observed features.

Alternative outflow parameters can better explain the Homunculus structure.

Abstract

In this work, we present new two-dimensional 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 10000 km s$^{-1}$, detected in recent observations, that provides 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 during 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 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.