123D Modelling of SN, NS and BH Progenitor Structures

Massive stars play a key role in the Universe through their strong radiative flux, the chemical elements they produce and the powerful explosions that mark their deaths. Theoretical models of massive stars are thus crucial to understand their properties, predict their fate and impact and provide a theoretical framework to interpret the huge datasets obtained with STFC-supported facilities (Gaia, JWST, LSST), maximising the return on these billion-pound investments. Large grids of stellar models predict how the properties and fate of stars depend on their initial mass and initial composition: supernova (SN) or not, neutron star (NS) or black hole (BH). The proposed SN/BH progenitor models will be of great interest for Gravitational Waves Astronomy as well as SN and stellar remnants research communities, tackling key questions like: "What is the distribution of BH masses and are there gaps in it?". Furthermore, this project will make extensive use of the STFC-supported DiRAC HPC facilities.

Due to the complexity of stars, stellar models would ideally be three-dimensional (3D) (magneto-)hydro-dynamic models that include all the relevant physics. 3D hydro models, however, must use time steps that are at most days. The total lifetime of stars, on the other hand, is at least millions of years. This explains why most stellar evolution models are limited to 1D, equivalent to limiting models to spherical symmetry (or averages). These 1D models have wide-ranging applications in astrophysics as explained above. The predictive power of 1D models, however, is crippled by 1D versions of 3D phenomena containing free parameters that need to be calibrated using observations. This project will focus on uncertainties related to convection since convection takes place in stars of all masses throughout their evolution and these uncertainties are unacceptably large.

This project will use synergy between 1D and 3D stellar models to assess the properties and impact of convection-driven asymmetries in massive stars and predict the structure of massive stars when their core is about to collapse to a NS or BH and possibly light up the "sky" with a so-called core-collapse supernova explosion (ccSN). By doing so, this project will provide next-generation "321D-guided" 1D pre-SN models and 3D synthetic initial conditions for ccSN simulations. These will enable an unprecedented study of the scale and impact of pre-SN asymmetries on SN and remnant properties across the massive star range. The new 1D and 3D SN/NS/BH progenitor structures and their spectroscopic signatures will be published to benefit the entire SN theory and observation communities. Furthermore, the improved treatment of convection in stellar models (which has been implemented in the open source MESA code) will benefit the entire community of 1D stellar evolution, with many applications in astrophysics.