Astrophysics at the Extremes: The Death of Massive Stars
Title: Astrophysics at the Extremes: The Death of Massive Stars
SNIC Project: SNIC 2019/3-394
Project Type: SNIC Medium Compute
Principal Investigator: Evan Patrick O'Connor <>
Affiliation: Stockholms universitet
Duration: 2019-08-01 – 2020-08-01
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 environments is core-collapse supernovae (CCSNe). A CCSN is an explosion that results when the iron core of a massive star collapses. A small fraction (~1%) of the gravitational binding energy released is used to turn the implosion into an explosion and an incredibly bright display of optical light. Research in this field, after over 50 years of intense study, is at a turning point in terms of our understanding. Modern simulations of CCSNe (including ones from the code used here) are readily achieving successful explosions, especially in 2D, but also, importantly, in 3D, allowing us to test these multidimensional simulations against observations and address several outstanding questions in the field of massive stars. This will be a remarkable step forward from the systematic, but parameterized, studies done in spherical symmetry up until now. We are now in a position to make precision and self-consistent predictions of many CCSN observables such as the explosion energy, success/failure landscape, and neutron star and black hole mass distributions. With this allocation, we propose to continue our exploration of the core collapse and the explosion phase of 100 stars in 2D proposed in SNIC 2018/3-638. We have had some setbacks which have somewhat hampered our progress but have also had new and exciting results. Some of the first progenitors we looked at in SNIC 2018/3-638 were on the extreme end. We found explosions in these progenitors but then following the evolution further showed the neutron star later collapses to a black hole. We have dubbed this scenario `explosive failure` and are eager to explore the astrophysical consequences. The issue we have uncovered is the difficulty to continue multidimensional simulations into the explosion phase with our full neutrino transport algorithms. We have spent considerable time understanding and now addressing this issue and aim to have a working solution by the end of the summer (1 month into this proposed allocation). The goal of the project is to determine which progenitor stars fail to explode and form black holes, which stars are successful and form neutron stars, and now, which stars successfully explode but still make black holes. A large number of simulations are needed since the explosion properties and dynamical behavior of the stars undergoing core collapse can dramatically vary with the initial mass of the star. We will make estimates of the final neutron star and black hole mass distributions for use in interpreting gravitational wave observations and allow us to address key questions such as the red supergiant problem. We will also simulate the evolution of the supernova shock through the progenitor star in order to capture the multidimensional structure of the innermost ejecta. This is especially important in our explosive failures where the explosion energy is less than the binding energy of the mantel of the star, meaning there will be significant fallback.