Astrophysics at the Extremes: The Death of Massive Stars
Title: Astrophysics at the Extremes: The Death of Massive Stars
SNIC Project: SNIC 2021/5-339
Project Type: SNIC Medium Compute
Principal Investigator: Evan Patrick O'Connor <>
Affiliation: Stockholms universitet
Duration: 2021-08-01 – 2022-07-01
Classification: 10305


Astrophysical environments at the extremes play crucial roles in astronomy, as well as being extraordinary laboratories for studying fundamental physics. One of these, Core-Collapse Supernovae (CCSNe) are explosions that result when a massive star collapses. Research in this field, after over 50 years of intense study, is at a turning point. Modern simulations of CCSNe (including ones by the PI) are readily achieving successful explosions, especially in 2D, but also, importantly, in 3D. What is learned from these simulations will represent a leap forward in our understanding. With this allocation, we propose to continue (see the activity report) our exploration of the CCSNe with the FLASH code. For this project period, we proposed three research directions for our multidimensional simulations in support of a VR Consolidator Grant obtained by the PI at the end of 2020. Aurore Betranhandy, a graduate student in the group, has been exploring the impact of particle microphysics on CCSNe. In the coming period, she will perform a suite of 2D simulations exploring the impact of axion emission in CCSNe. Axions are theoretical particles proposed to solve the strong CP problem (i.e. why the Universe is made of matter instead of antimatter), axions are also a potential dark matter candidate. To date, there have only been explorations of the impact of axions on CCSNe via spherically symmetric simulations and, except for one study, only done as a post-processing step, therefore any dynamical feedback on the system is ignored. The outcome of this study will show, for a given coupling constant, at what level axions can impact the dynamics of the explosion. With our previous allocation, one of the group's postdoctoral researchers, Andre Schneider, used FLASH to perform a suite of failed supernovae simulations, with subsequent whole star simulations to follow what happens in spherical symmetry. With this requested allocation, the new project postdoc will take select models from this suite and perform simulations to gauge the multidimensional impact on the final black hole mass distribution, important deliverables of the PI's VR consolidator grant. This will be a suite of 2D models from which we will further select individual models for potential exploration in 3D. Our recent work in Eggenberger Andersen et al., performed on SNIC resources, has revealed the interesting dynamics that give rise to gravitational waves. By far, the biggest limitation of this work was that it was performed in 2D. As part of this next allocation period, we proposed to explore several proposed gravitational wave emission mechanisms in 3D as a follow-up to this recent work. This will involve new 3D simulations (by a new PhD student in the group), which will require significantly more resources. We will also use these simulations as a benchmark to achieve the goals of the PI's VR consolidator grant, which is to produce 3D simulations with efficient neutrino transport and lower computational cost. We have done 3D with the previous allocation and discuss the results in the resource section.