Nucleosynthesis in thermonuclear supernovae with tracers: convergence and variable mass particles

TL;DR

This study examines the number of tracer particles needed for accurate nucleosynthesis predictions in supernova simulations, introducing variable tracer masses to improve yield convergence, and finds that fewer particles suffice for most isotopes.

Contribution

It demonstrates that a small number of tracer particles can reliably predict nucleosynthetic yields and introduces a variable mass tracer approach for better outer layer resolution.

Findings

Fewer than 32 tracers per axis are sufficient for most abundant isotopes.

Variable tracer mass distribution improves outer layer yield convergence.

Existing simulations likely used adequate tracer numbers for integrated yields.

Abstract

Nucleosynthetic yield predictions for multi-dimensional simulations of thermonuclear supernovae generally rely on the tracer particle method to obtain isotopic information of the ejected material for a given supernova simulation. We investigate how many tracer particles are required to determine converged integrated total nucleosynthetic yields. For this purpose, we conduct a resolution study in the number of tracer particles for different hydrodynamical explosion models at fixed spatial resolution. We perform hydrodynamic simulations on a co-expanding Eulerian grid in two dimensions assuming rotational symmetry for both pure deflagration and delayed detonation Type Ia supernova explosions. Within a given explosion model, we vary the number of tracer particles to determine the minimum needed for the method to give a robust prediction of the integrated yields of the most abundant nuclides. For the first time, we relax the usual assumption of constant tracer particle mass and introduce a radially vary- ing distribution of tracer particle masses. We find that the nucleosynthetic yields of the most abundant species (mass fraction > 10E-5) are reasonably well predicted for a tracer number as small as 32 per axis and direction - more or less independent of the explosion model. We conclude that the number of tracer particles that were used in extant published works appear to have been sufficient as far as integrated yields are concerned for the most copiously produced nuclides. Additionally we find that a suitably chosen tracer mass distribution can improve convergence for nuclei produced in the outer layer of the supernova where the constant tracer mass prescription suffers from poor spatial resolution.