Recovery from Giant Eruptions in Very Massive Stars

We use a hydro-and-radiative-transfer code to explore the behavior of a very massive star (VMS) after a giant eruption -- i.e., following a supernova impostor event. Beginning with reasonable models for evolved VMSs with masses of $80~M_\odot$ and $120~M_\odot$, we simulate the change of state caused by a giant eruption via two methods that explicitly conserve total energy: 1. Synthetically removing outer layers of mass of a few $M_\odot$ while reducing the energy of the inner layers. 2. Synthetically transferring energy from the core to the outer layers, an operation that automatically causes mass ejection. Our focus is on the aftermath, not the poorly-understood eruption itself. Then, using a radiation-hydrodynamic code in 1D with realistic opacities and convection, the interior disequilibrium state is followed for about 200 years. Typically the star develops a $\sim 400 ~\rm{km}~\rm{s}^{-1}$ wind with a mass loss rate that begins around $0.1 ~M_\odot~\rm{yr^{-1}}$ and gradually decreases. This outflow is driven by $κ$-mechanism radial pulsations. The 1D models have regular pulsations but 3D models will probably be more chaotic. In some cases a plateau in the mass-loss rate may persist about 200 years, while other cases are more like $η$ Car which lost $>10~M_\odot$ and then had an abnormal mass loss rate for more than a century after its eruption. In our model, the post-eruption outflow carried more mass than the initial eruption. These simulations constitute a useful preliminary reconnaissance for 3D models which will be far more difficult.

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