Fast ejecta resulted from jet-wind interaction in the Great Eruption of Eta Carinae

The accretion model for the 19th century Great Eruption (GE) of η Carinae suggests that mass outflowing from the primary was accreted on to the secondary, and the gravitational energy of that mass accounts for the increase in luminosity and most of the kinetic energy of the ejecta. It further argues that the accretion was accompanied by the ejection of two jets that shaped the bipolar Homunculus nebula. Observations of echos from the GE found emission lines with broad wings suggesting some of the mass in equatorial directions reached more than 10 000 km s-1. We run hydrodynamic simulations following periastron passage during the GE, launching jets from the secondary as it accreted gas erupted from the primary. We then follow the interaction of the polar jets with the surrounding primary wind, as they accelerate part of the flow to velocities >10 000 km s-1 and deflect it towards lower latitudes. We find that the amount of mass that reached these high velocities during the GE is Mh ≈ 0.02 M⊙. This value reaches maximum and then decreases with time. Our simulations agree with previous results of the accretion model from which we estimate Mh taking into account the energy budget of the GE. The accretion model can explain the observations of high velocity gas in light echos with the known two stars, and a triple star system is not required.