Accretion at the periastron passage of Eta Carinae

TL;DR

This study uses high-resolution hydrodynamical simulations to demonstrate that accretion onto the secondary star occurs during periastron in Eta Carinae, influenced by gravitational attraction and instabilities in colliding stellar winds.

Contribution

First detailed hydrodynamical simulations including self-gravity and cooling show accretion phenomena during Eta Carinae's periastron passage, highlighting the impact of stellar mass on accretion.

Findings

Accretion occurs a few days before periastron.

More massive secondary stars experience more pronounced accretion.

Instabilities lead to filament and clump formation in colliding winds.

Abstract

We present high resolution numerical simulations of the colliding wind system $\eta$ Carinae, showing accretion onto the secondary star close to periastron passage. Our hydrodynamical simulations include self gravity and radiative cooling. The smooth stellar winds collide and develop instabilities, mainly the non-linear thin shell instability, and form filaments and clumps. We find that a few days before periastron passage the dense filaments and clumps flow towards the secondary as a result of its gravitational attraction, and reach the zone where we inject the secondary wind. We run our simulations for the conventional stellar masses, $M_1=120 ~\rm{M_\odot}$ and $M_2=30 ~\rm{M_\odot}$, and for a high mass model, $M_1=170 ~\rm{M_\odot}$ and $M_2=80 ~\rm{M_\odot}$, that was proposed to better fit the history of giant eruptions. As expected, the simulations results show that the accretion processes is more pronounced for a more massive secondary star.