The evolution and impact of 3000 M$_\odot$ stars in the early Universe

TL;DR

This paper models the evolution of extremely massive Population III stars up to 3000 solar masses, exploring their internal structure, surface composition, and potential feedback effects on early universe environments.

Contribution

It provides detailed evolutionary models of the most massive Population III stars, including their internal mixing, surface helium enrichment, and potential role in early cosmic chemical enrichment.

Findings

Final surface helium abundance of 0.74 in 3000 Msol model

Star's evolution impacts early universe chemical enrichment

High N/O ratio consistent with observations of high-redshift galaxy GN-z11

Abstract

We present evolutionary models of massive, accreting population III stars with constant and variable accretion rates until the end of silicon burning, with final masses of 1000 - 3000 Msol. In all our models, after the core-hydrogen-burning phase, the star expands towards the red side of the Hertzsprung-Russell diagram is where it spends the rest of its evolution. During core helium burning, the models exhibit an outer convective envelope as well as many large intermediate convective zones.These intermediate zones allow for strong internal mixing to occur which enriches the surface in helium. The effect of increasing metallicity at a constant accretion rate of 10^{-3} Msol/yr shows an increase in the lifetime, final mass and distribution of helium in the envelope. Our fiducial model with mass of 3000 Msol has a final surface helium abundance of 0.74 and 9% of its total mass or 50% of the core mass, has a value of Gamma1 < 4/3 at the end of core silicon burning. If the collapse of the core is accompanied by the ejection of the envelope above the carbon-oxygen core, this could have a significant impact on the chemical evolution of the surroundings and subsequent stellar generations. The model has a final log(N/O) ~ 0.45, above the lower limit in the recently detected high-redshift galaxy GN-z11. We discuss the impact of a single 3000 Msol star on chemical, mechanical and radiative feedback, and present directions for future work.