Evolution of 3-9 Mo Stars for Z=0.001 - 0.03 and Metallicity Effects on Type Ia Supernovae

TL;DR

This study investigates how stellar mass and metallicity influence the C/O ratio in white dwarf progenitors, affecting Type Ia supernovae properties and their use in cosmology.

Contribution

It provides a systematic analysis of stellar evolution for 3-9 solar masses across various metallicities, revealing how these factors impact SN Ia progenitor characteristics.

Findings

C/O ratio varies between 0.36 and 0.5 before explosion

Maximum progenitor mass decreases with lower metallicity

Metallicity effects are crucial for accurate SN Ia progenitor estimates

Abstract

Recent observations have revealed that Type Ia supernovae (SNe Ia) are not perfect standard candles but show some variations in their absolute magnitudes, light curve shapes, and spectra. The C/O ratio in the SNe Ia progenitors (C-O white dwarfs) may be related to this variation. In this work, we systematically investigate the effects of stellar mass (M) and metallicity (Z) on the C/O ratio and its distribution in the C-O white dwarfs by calculating stellar evolution from the main-sequence through the end of the second dredge-up for M=3-9 Mo and Z=0.001-0.03. We find that the total carbon mass fraction just before SN Ia explosion varies in the range 0.36 -- 0.5. We also calculate the metallicity dependence of the main-sequence-mass range of the SN Ia progenitor white dwarfs. Our results show that the maximum main-sequence mass to form C-O white dwarfs decreases significantly toward lower metallicity, and the number of SN Ia progenitors may be underestimated if metallicity effectis neglected. We discuss the implications of these results on the variation of SNe Ia, determination of cosmological parameters, luminosity function of white dwarfs, and the galactic chemical evolution.