Type IIP Supernova Progenitors and their explodability I: Convective Overshoot, Blue Loops and Surface Composition

TL;DR

This study investigates how convective overshoot influences the evolution, surface composition, and explodability of massive star progenitors of type IIP supernovae, using MESA models and focusing on SN 2013ej.

Contribution

It demonstrates the impact of moderate convective overshoot on blue loop formation and explores how overshoot affects supernova progenitor explodability parameters.

Findings

Moderate overshoot causes blue loops in stellar evolution.

Surface CNO abundances show enrichment patterns during evolution.

Models with certain overshoot parameters are likely to explode.

Abstract

We present the evolution of massive star progenitors of supernovae of type IIP. We take the example of the nearby and well-studied SN 2013ej. We explore how convective overshoot affects the stellar structure, surface abundances, and effective temperature of massive stars, using the Modules for Experiments in Stellar Astrophysics (MESA). In particular models with moderate overshoot ($f$ = 0.02 to 0.031) show the presence of blue loops in the Hertzsprung-Russell diagram with a red to blue [$log_{10}(T_{eff}/\rm K)$ from $< 3.6$ to $> 4.0$] excursion and transition back to red, during core helium burning phase. Models with overshoot outside this range of $f$ values kept the star in the red supergiant state throughout the post helium ignition phases. The surface CNO abundance shows enrichment post-main-sequence and again around the time when helium is exhausted in core. These evolutionary changes in surface CNO abundance are indistinguishable in the currently available observations due to large observational uncertainties. However, these observations may distinguish between the ratios of surface nitrogen to oxygen at different evolutionary stages of the star. We also compare the effects of convective overshoot on various parameters related to likelihood of explosion of a star as opposed to collapse to a black hole. These parameters are the compactness parameter, M$_4$, and $\mu_4$. Combination $\mu_4 \times $M$_4$, and $\mu_4$ have similar variation with $f$ and both peak out at $f$ = 0.032. We find that all of our 13 M$_{\odot}$ models are likely to explode.