Simulating the formation of Eta Carinae's surrounding nebula

TYPEAstrophysics Seminar
Speaker:Ryosuke Hirai
Affiliation:Monash University
LocationZoom LINK


Eta Carinae is one of the most extraordinary stars known in our galaxy, having many peculiar properties. One of the most prominent features is that it is surrounded by bipolar lobes called the Homunculus nebula. This nebula originated from the Great Eruption in 1844 that was visible to the naked eye. It is also known that Eta Car had other small eruptions centuries before the Great Eruption, where smaller ejectiles were emitted with ~300 year intervals. Many attempts have been made to understand the formation of Eta Car and its many peculiar properties, with different degrees of success. Here we focus on a scenario starting with a hierarchical triple system. I will discuss results of 2.5D hydrodynamical simulations of the outflow from a stellar merger and show that it can closely reproduce the morphology of the observed Homunculus nebula. I will also discuss how close periastron encounters in triple systems can reproduce the Outer Ejecta via n-body simulations. Stellar mergers in triple systems are probably not as rare as previously considered. Understanding the formation of Eta Carinae may help us understand the formation and evolution of LBVs in general, and possibly many other peculiar objects involving mergers.