The correlation between C/O ratio, metallicity and the initial WD mass for SNe Ia

TL;DR

This study investigates how initial metallicity influences carbon abundance in white dwarfs and its subsequent effect on nickel-56 production, potentially explaining variations in Type Ia supernova luminosity.

Contribution

It reveals the metallicity-dependent behavior of carbon abundance in white dwarfs and links initial progenitor parameters to supernova explosion outcomes.

Findings

Carbon abundance is independent of metallicity for Z ≤ 0.02.

Higher metallicity leads to lower carbon abundance at fixed WD mass when Z > 0.02.

Metallicity and carbon abundance jointly affect $^{56}$Ni production, influencing supernova brightness.

Abstract

In this paper, we want to check whether or not the carbon abundance can be affected by initial metallicity. We calculated a series of stellar evolution. We found that when $Z\leq0.02$, the carbon abundance is almost independent of metallicity if it is plotted against the initial WD mass. However, when $Z>0.02$, the carbon abundance is not only a function of the initial WD mass, but also metallicity, i.e. for a given initial WD mass, the higher the metallicity, the lower the carbon abundance. Based on some previous studies, i.e. both a high metallicity and a low carbon abundance lead to a lower production of $^{\rm 56}$Ni formed during SN Ia explosion, the effects of the carbon abundance and the metallicity on the amount of $^{\rm 56}$Ni are enhanced by each other, which may account for the variation of maximum luminosity of SNe Ia, at least qualitatively. Considering that the central density of WD before supernova explosion may also play a role on the production of $^{\rm 56}$Ni and the carbon abundance, the metallicity and the central density are all determined by the initial parameters of progenitor system, i.e. the initial WD mass, metallicity, orbital period and secondary mass, the amount of $^{\rm 56}$Ni might be a function of the initial parameters. Then, our results might construct a bridge linking the progenitor model and the explosion model of SNe Ia.