The Last Minutes of Oxygen Shell Burning in a Massive Star (1605.01393v2)

Abstract: We present the first 3D simulation of the last minutes of oxygen shell burning in an 18 solar mass supernova progenitor up to the onset of core collapse. A moving inner boundary is used to accurately model the contraction of the silicon and iron core according to a 1D stellar evolution model with a self-consistent treatment of core deleptonization and nuclear quasi-equilibrium. The simulation covers the full solid angle to allow the emergence of large-scale convective modes. Due to core contraction and the concomitant acceleration of nuclear burning, the convective Mach number increases to ~0.1 at collapse, and an l=2 mode emerges shortly before the end of the simulation. Aside from a growth of the oxygen shell from 0.51 to 0.56 solar masses due to entrainment from the carbon shell, the convective flow is reasonably well described by mixing length theory, and the dominant scales are compatible with estimates from linear stability analysis. We deduce that artificial changes in the physics, such as accelerated core contraction, can have precarious consequences for the state of convection at collapse. We argue that scaling laws for the convective velocities and eddy sizes furnish good estimates for the state of shell convection at collapse and develop a simple analytic theory for the impact of convective seed perturbations on shock revival in the ensuing supernova. We predict a reduction of the critical luminosity for explosion by 12--24% due to seed asphericities for our 3D progenitor model relative to the case without large seed perturbations.

Insightful Overview of the Paper "The Last Minutes of Oxygen Shell Burning in a Massive Star"

"The Last Minutes of Oxygen Shell Burning in a Massive Star" by Müller et al. presents a detailed $4\pi$-3D simulation paper of the concluding phases of oxygen shell burning in an $18 M_\odot$ supernova progenitor. This paper discusses critical aspects of the simulation methodology, key findings, and the implications for understanding the mechanisms behind core-collapse supernovae.

The authors simulate the dynamics of oxygen shell burning in three dimensions using a full $4\pi$ coverage. A moving inner boundary approach is employed to model accurately the contraction phases of the silicon and iron core, referencing a 1D stellar evolution background model. The researchers emphasize capturing large-scale convective modes by simulating the entire solid angle. This facilitates accurate modeling of convective Mach numbers, which rise to around 0.1 as core collapse approaches, with an emergence of a significant $\ell=2$ mode.

A notable feature of this paper is the simulation's treatment of the oxygen shell, which grows from $0.51 M_\odot$ to $0.56 M_\odot$ by the ingestion of material from the overlying carbon shell. The authors effectively argue that this convective behavior aligns with predictions from mixing length theory (MLT) and linear stability analysis.

The implications proposed by this simulation paper are significant for understanding core-collapse supernovae. Artificial modifications in core contraction physics are revealed to potentially have significant impacts on convection states at collapse. The authors propose that scaling laws can provide reliable estimates of convective velocities and eddy sizes, critical for predicting supernova shock revival.

The paper makes a bold claim regarding the likely reduction of critical luminosity needed for explosion by 12 to 24% due to seed asphericities for the 3D progenitor model, compared to cases without large seed perturbations. The potential reduction in critical luminosity aligns with their argument that progenitor asphericities can considerably assist in facilitating shock revival.

The broader implications of this research span both practical and theoretical realms. Practically, this simulation offers a sophisticated model that can serve as a basis for future core-collapse supernova studies. Theoretically, these findings urge a re-evaluation of the treatment of shell convection in stellar evolution models, hinting at the necessity for including full solid-angle simulations to adequately capture emergent large-scale modes.

As the field progresses, advanced simulations such as those presented in this paper are likely to contribute toward more accurate predictions of supernovae outcomes and dynamics. Future developments in AI and computational astrophysics could facilitate even higher resolution simulations, providing deeper insights into the final evolutionary stages of massive stars.

In sum, Müller et al.'s paper provides a comprehensive examination of late-stage oxygen shell burning in massive stars, with results that offer a promising avenue for enhancing our understanding of the progenitor dynamics leading up to supernova explosions. The authors lay an important groundwork for future explorations into the complex interplay of nuclear burning, convective processes, and stellar core dynamics through multidimensional simulation frameworks.