A novel mathematical technique for radioactive decay computations in supernovae simulation

Supernovae are the explosive deaths of stars with energies that allow the creation of heavy elements. They are important end-points of stellar evolution, and the elements synthesized in the explosion are crucial for the formation of earth-like planets and ultimately life as we know it. The decay of nickel and cobalt, which are synthesized in supernovae explosions, generate high-energy photons which are reprocessed into optical wavelengths by the supernova’s ejecta. Simulating these decay processes calculate the energy available for deposition into the material of the ejecta. The linear ODEs describing such decays are traditionally solved using an iterative process. In this presentation, I will describe a novel technique, using linear algebra and consisting of a coordinate transformation to uncouple these ODEs, used by the python package radioactivedecay. I extended the use of this technique in radioactivedecay to stable nuclides, which themselves scatter photons in the ejecta of supernovae. These calculations will be used as a means to calculate the abundances of fundamental isotopes such as nickel, cobalt, and iron in the open-source supernova simulation program TARDIS, and will allow for fast and accurate decay calculations to be performed at the TARDIS simulation’s runtime.