Astrophysics at the Extremes: The Death of Massive Stars
Title: Astrophysics at the Extremes: The Death of Massive Stars
SNIC Project: SNIC 2020/6-161
Project Type: SNIC Medium Storage
Principal Investigator: Evan Patrick O'Connor <>
Affiliation: Stockholms universitet
Duration: 2020-08-17 – 2021-08-01
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, Core-Collapse Supernovae (CCSNe) are explosions that result when the iron core of 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 from the code used here) are readily achieving successful explosions, especially in 2D, but also, importantly, in 3D, allowing us to now test theories of massive stars and compare with observations. This will be a remarkable step forward from the systematic, but parameterized, studies done in spherical symmetry up until now. With this allocation, we propose to continue (see the activity report) our exploration of the CCSNe at the extremes. For this project period, we proposed three research directions for our multidimensional simulations. Aurore Betranhandy, a graduate student in the group, has been exploring the impact of magnetic fields on the neutrino cross-sections and the relation to hypernovae, an extreme subclass of supernovae connected to long gamma-ray burst. The quantization of the electron energy levels in the presence of strong magnetic fields causes the neutrino opacity to change. She will perform a suite of 2D magnetohydrodynamic simulations of rotating core-collapse supernovae to test these interactions for the first time in the core-collapse context. A prediction is an impact on the composition of the outflows, which for these hypernovae candidates include an r-process component. By varying rotation (no, slow, and fast) and magnetic field strength (no, low, and high) for several progenitors (low mass and high mass progenitors), we will map out the potential phase space, we estimate ~20 2D simulations. Second, a postdoctoral researcher in our group, Shuai Zha, has created new electron-capture supernova progenitor models in multiple dimensions, for the first time. As part of this project, Shuai will perform 2D simulations of the explosion and also 2D whole-star simulations following the shock through the rest of the progenitor star to estimate final explosion properties and multidimensional remnant structure. We will test several models with several realizations of convection and turbulence, totaling ~20 simulations. We will also use these progenitor models for exploratory, low-resolution simulations in 3D in preparation for a larger proposal in the future. Finally, our group, led by myself and another postdoctoral researcher, Andre Schneider, will use FLASH to explore black hole formation in 2D simulations, both of the core-collapse itself and also whole-star simulations. We will use the results to make estimates on the final black hole mass distribution and use them to interpret the astrophysical origin of the black holes that are being discovered by the LIGO and Virgo gravitational wave observatories. We will explore a suite of progenitors stars (~5) and equations of state (~4) based on the results of extensive 1D simulations we have recently published for a total of ~20 2D simulations.