The influence of rotation and metallicity on the explodability of massive stars

TL;DR

This work analyzes how rotation and metallicity influence the explodability of massive stars by coupling MESA pre-collapse evolution (with $V_{ini}\in\{0,300,600\}$ km s$^{-1}$ and $Z\in\{Z_{\odot},1/10Z_{\odot},1/50Z_{\odot}\}$) to GR1D core-collapse simulations to determine a critical neutrino heating parameter and the corresponding time-averaged heating efficiency. By mapping explosion outcomes to the compactness parameter $ξ_{2.5}$ and to ZAMS/CO-core masses, under LS220 EOS, the study derives revised explodability criteria: $ξ_{2.5}=0.45$ for non-rotating, $0.48$ for $V_{ini}=300$ km s$^{-1}$, $0.47$ for $V_{ini}=600$ km s$^{-1}$ at solar metallicity, and $0.59$ at low metallicity (CHE cases). CHE in rapidly rotating, low-$Z$ stars significantly expands the explosion-prone regime and narrows the FSN mass windows, while rotation raises the upper compactness threshold for explosions; these results emphasize the necessity of including rotation and metallicity in progenitor models and in interpreting CCSN outcomes and potential long gamma-ray bursts.

Abstract

During the late stages of massive stellar evolution, failed supernovae (FSN) may form through core-collapse processes. The traditional evaluation criterion $ξ_{2.5}$ $=$ 0.45, primarily established using non-rotating progenitor models, suffers from significant inaccuracies when applied to rotating pre-supernova systems. The effects of metallicity and rotation on the explodability landscapes of massive stars lack robust quantification. We aim to investigate how rotation and metallicity influence the explodability of massive stars. We investigate how rotation and metallicity affect stellar explodability using MESA simulations with initial rotational velocities of $0$, $300$, and $600~\mathrm{km,s^{-1}}$ at three metallicities ($Z_{\odot}$, $1/10,Z_{\odot}$, $1/50,Z_{\odot}$). Core-collapse phases are simulated with GR1D to determine critical heating efficiencies. Our results yield revised $ξ_{2.5}$ criteria: 0.45 for non-rotating models; 0.48 for $300~\mathrm{km,s^{-1}}$; 0.47 for $600~\mathrm{km,s^{-1}}$ at solar metallicity; and 0.59 for low-metallicity models. Chemically homogeneous evolution in rapidly rotating low-metallicity stars significantly raises the compactness limit for successful explosions and narrows the zero-age main sequence mass range for failed supernovae. Rotation substantially affects the explodability of low-metallicity massive stars, underscoring the importance of incorporating rotational effects in models of core-collapse supernova progenitors.

Figures (8)

• Figure 1: The shock wave radius evolution versus explosion time $t_{\mathrm{bounce}}$ for different $f_{\mathrm{heat}}$ values. Simulations start with an iron core collapse velocity of 1000 km s$^{-1}$, where $t=0$ corresponds to shock wave formation. Top and bottom panels show 15 M$_{\odot}$ and 60 M$_{\odot}$ ZAMS masses respectively, with initial velocities $V_{\mathrm{ini}} = 0$ (left panels) and 300 km s$^{-1}$ (right panels). All models have $1/10$ Z$_{\odot}$ metallicity.
• Figure 2: For $f_{\mathrm{heat}} = f_{\mathrm{heat}}^{\mathrm{crit}}$, evolution of electron neutrino and antineutrino luminosities $L_{\bar{\nu}_e,\nu_e}$ (solid lines) at the gain radius and net neutrino energy deposition rate in the gain layer $\dot{Q}_{\nu}$ ($\int_{\text{gain}} \dot{q}^{+}_{v} \, dV$, dashed lines) versus time $t_{\mathrm{bounce}}$. Simulations start with an iron core collapse velocity of 1000 km s$^{-1}$, where $t=0$ corresponds to shock wave formation. Top and bottom panels show 15 M$_{\odot}$ and 60 M$_{\odot}$ ZAMS masses respectively, with initial velocities $V_{\mathrm{ini}} = 0$ (left panels) and 300 km s$^{-1}$ (right panels). All models have $1/10$ Z$_{\odot}$ metallicity.
• Figure 3: The central angular velocity ($\omega_{c}$) at pre-supernova star for different ZAMS mass models versus various $V_{\mathrm{ini}}$ and metallicities. The left and right panels represent $V_{\mathrm{ini}}$ = 300 km s$^{-1}$ and $V_{\mathrm{ini}}$ = 600 km s$^{-1}$, respectively. Red, green, and black represent metallicities of $Z_{\odot}$, $1/10$$Z_{\odot}$, and $1/50$$Z_{\odot}$, respectively. Squares mark the occurrence of CHE.
• Figure 4: The compactness parameter $\xi_{\mathrm{2.5}}$ versus the critical model's time-averaged heating efficiency $\bar{\eta}_{\mathrm{heat}}^{\mathrm{crit}}$. Panels left, center, and right correspond to initial velocities $V_{\mathrm{ini}}$ = 0, 300 km s$^{-1}$, and 600 km s$^{-1}$, respectively. Data points in red, green, and black denote metallicities $Z_{\odot}$, 1/10 $Z_{\odot}$, and 1/50 $Z_{\odot}$. Squares mark the occurrence of CHE. The hollow inverted triangles are calculated by 2011ApJ...730...70O, with red, green, and black colors representing the combinations of EOS and models: LS220-sWH07, LS180-sWH07, and LS220-uWHW02, respectively.
• Figure 5: The $\xi_{\mathrm{2.5}}$ versus initial mass for models with varying initial rotational velocities $V_{\rm ini}$ and metallicities. The left, middle, and right panels correspond to models with $V_{\mathrm{ini}} = 0$, $300\,\mathrm{km\,s^{-1}}$, and $600\,\mathrm{km\,s^{-1}}$, respectively. Red, green, and black data points represent metallicities of $Z_{\odot}$, $1/10\,Z_{\odot}$, and $1/50\,Z_{\odot}$, respectively. Squares mark the occurrence of CHE. The left and middle blue triangles indicate model calculations from 2023ApJ...952...79L ($Z = 0.0017$), while the right blue triangle denotes the rapidly rotating model from 2020ApJ...901..114A ($1/50\,Z_{\odot}$). Dashed lines mark explosion criteria for $\xi_{2.5}$: the black line from 2011ApJ...730...70O, and others from our results.