Numerical modeling of the 1840s major eruption of η Carinae as an explosion

In this paper, new two-dimensional hydrodynamical simulations of eta Car's nebulae are performed. In the 1840s, the massive star eta Car suffered a major eruption that resulted in the formation of a bipolar structure, which is commonly known as the large Homunculus. During this event, eta Car expelled into the circumstellar material a total mass of similar to 10 M-circle dot and released a total energy of E-k similar to 10(50) erg over a very short time (<= 5 yr). These kinds of explosive events are frequently called supernova impostors due to their resemblance to a type II supernova, but the stars survive the explosion. In the case of eta Car, a brief explosion scenario provides a potential explanation for the behavior of the historical light curve of eta Car a few years (similar to 10 yr) after the nineteenth century outburst. Here, such an alternative scenario of an explosion is assumed (instead of a super-Eddington wind) in order to investigate whether an explosive event is also able to explain the shape and kinematics of the large Homunculus. I show that the numerical simulations presented here indeed resemble some of the observed features of the nebula, such as the present-day double-shell structure of the Homunculus, with a thin outer dense shell and a thicker inner layer, as well as thermal instabilities (Rayleigh-Taylor and Kelvin-Helmholtz) along the dense shell that may lead to the current mottled appearance of the large Homunculus. Nonetheless, the explosion model for the 1840s major eruption of eta Car is not able to account for the estimated age of the large Homunculus.