Higgins, ER, Sander, AAC, Vink, JS and (2021) Evolution of Wolf-Rayet stars as black hole progenitors. Monthly Notices of the Royal Astronomical Society. (In Press)

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## Abstract

Evolved Wolf-Rayet stars form a key aspect of massive star evolution, and their strong outflows determine their final fates. In this study, we calculate grids of stellar models for a wide range of initial masses at five metallicities (ranging from solar down to just 2 per cent solar). We compare a recent hydrodynamically-consistent wind prescription with two earlier frequently-used wind recipes in stellar evolution and population synthesis modelling, and we present the ranges of maximum final masses at core He-exhaustion for each wind prescription and metallicity Z. Our model grids reveal qualitative differences in mass-loss behaviour of the wind prescriptions in terms of “convergence”. Using the prescription from Nugis &amp; Lamers the maximum stellar black hole is found to converge to a value of 20-30 $\rm M_ødot$, independent of host metallicity, however when utilising the new physically-motivated prescription from Sander &amp; Vink there is no convergence to a maximum black hole mass value. The final mass is simply larger for larger initial He-star mass, which implies that the upper black hole limit for He-stars below the pair-instability gap is set by prior evolution with mass loss, or the pair instability itself. Quantitatively, we find the critical Z for pair-instability (ZPI) to be as high as 50 per cent $\rm Z_ødot$, corresponding to the host metallicity of the LMC. Moreover, while the Nugis &amp; Lamers prescription would not predict any black holes above the approx 130 $\rm M_ødot$ pair-instability limit, with Sander &amp; Vink winds included, we demonstrate a potential channel for very massive helium stars to form such massive black holes at ∼ 2 per cent $\rm Z_ødot$ or below.

Item Type: Article This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2021 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Q Science > QB Astronomy > QB799 Stars Faculty of Natural Sciences > School of Chemical and Physical Sciences Symplectic 08 Jun 2021 13:09 08 Jun 2021 13:10 https://eprints.keele.ac.uk/id/eprint/9696

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