Impact of convective overshooting on the single-degenerate model of Type Ia supernovae

¹ International Centre of Supernovae (ICESUN), Yunnan Key Laboratory of Supernova Research, Yunnan Observatories, Chinese Academy of Sciences (CAS), Kunming 650216, China
² University of Chinese Academy of Sciences, Beijing 100049, PR China

^⋆ Corresponding authors: wangxinghuan@ynao.ac.cn, xiangcunmeng@ynao.ac.cn

Received: 10 March 2025
Accepted: 8 May 2025

Abstract

Context. The single-degenerate (SD) model is one of the principal models for the progenitors of Type Ia supernovae (SNe Ia). However, it faces some challenges, the primary being its inability to account for the observed SN Ia birth rate. Many studies have attempted to address this issue by expanding the parameter space, defined by the initial donor star mass and orbital period, that can lead to SNe Ia, as well as by improving binary population synthesis. While these efforts have led to significant progress, many uncertainties in stellar physics persist, which influences the outcomes of such studies. Convective overshooting, which can significantly affect the internal structure of a star and subsequently its evolution within a binary system, is one of the most significant sources of uncertainty in stellar physics.

Aims. We investigate the effect of convective overshooting on the parameter space and birth rate of SNe Ia within the SD model.

Methods. We employed the common-envelope wind (CEW) model, a new version of the SD model, as our progenitor model. Using MESA, we obtained the parameter space that leads to SNe Ia for three different convective overshooting parameters and calculated the corresponding SN Ia birth rate.

Results. Convective overshooting expands the upper boundaries (corresponding to a larger initial donor mass) and right boundaries (corresponding to a longer initial orbital period) of the parameter space for systems with massive white dwarfs (WDs; ≥0.75 M_⊙). However, the minimum WD mass and the parameter space for low-mass WDs – and, consequently, the calculated SN Ia birth rate – vary non-monotonically with convective overshooting parameters. The CEW model may explain the SNe Ia that interact with the circumstellar medium (CSM), i.e., SNe Ia-CSM. We find that the parameter space for SNe Ia-CSM increases with convective overshooting parameters, as does their birth rate.