# Critical accretion rates for rapidly growing massive Population III stars

**Authors:** Devesh Nandal, John A. Regan, Tyrone E. Woods, Eoin Farrell, Sylvia Ekström, Georges Meynet  
**arXiv:** [2306.17223](https://arxiv.org/abs/2306.17223)  
**Date:** 2023-06-29  
**Summary page:** https://www.summarizepaper.com/en/paper/2306.17223v1/

## Key points

- Study investigates evolution of Population III stars under variable accretion rates
- Ten models with varying accretion histories simulated, covering final mass range from 491 M$_{\odot}$ to 6127 M$_{\odot}$
- Critical accretion rate separates red and blue supergiant regimes during pre-main sequence evolution
- Critical accretion rate approximately $2.5\times10^{-2}$ M$_{\odot}$/yr, drops to $7.0\times10^{-3}$ M$_{\odot}$/yr once core hydrogen burning begins
- Variable accretion rates significantly impact various aspects of Population III star evolution including lifetimes, surface enrichment, final mass, and time spent in red phase
- Kelvin-Helmholtz timescale in outer surface layers more relevant for determining transition between red and blue phases than luminosity wave encountered during early pre-main sequence evolution
- Research provides comprehensive understanding of how Population III stars evolve under different accretion rates
- Findings have implications for understanding the role of these stars in shaping the cosmos and studying the evolution and fate of massive black holes in the early Universe.

## Summary

This study investigates the evolution of Population III stars under variable accretion rates. Using the Geneva stellar evolution code, ten models with varying accretion histories are simulated, covering a final mass range from 491 M$_{\odot}$ to 6127 M$_{\odot}$. The findings reveal that there is a critical accretion rate that separates the red and blue supergiant regimes during the pre-main sequence evolution. This critical accretion rate is approximately $2.5\times10^{-2}$ M$_{\odot}$/yr; however, once core hydrogen burning begins, this critical accretion rate drops to $7.0\times10^{-3}$ M$_{\odot}$/yr. Furthermore, it is demonstrated that variable accretion rates significantly impact various aspects of Population III star evolution including lifetimes, surface enrichment, final mass and time spent in the red phase. Additionally, the study confirms that the Kelvin-Helmholtz timescale in the outer surface layers is more relevant for determining the transition between red and blue phases than the luminosity wave encountered during early pre-main sequence evolution. Overall, this research provides a comprehensive understanding of how Population III stars evolve under different accretion rates and contributes to our current knowledge of early stellar evolution. These findings have implications for our understanding of the role of these stars in shaping the cosmos and highlight the importance of considering variable accretion rates when studying the evolution and fate of massive black holes in the early Universe.