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Is GW190521 the merger of black holes from the first stellar generations?

Farrell, Eoin; Groh, Jose H; Hirschi, Raphael; Murphy, Laura; Kaiser, Etienne; Ekström, Sylvia; Georgy, Cyril; Meynet, Georges

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Authors

Eoin Farrell

Jose H Groh

Laura Murphy

Etienne Kaiser

Sylvia Ekström

Cyril Georgy

Georges Meynet



Abstract

GW190521 challenges our understanding of the late-stage evolution of massive stars and the effects of the pair-instability in particular. We discuss the possibility that stars at low or zero metallicity could retain most of their hydrogen envelope until the pre-supernova stage, avoid the pulsational pair-instability regime and produce a black hole with a mass in the mass gap by fallback. We present a series of new stellar evolution models at zero and low metallicity computed with the Geneva and MESA stellar evolution codes and compare to existing grids of models. Models with a metallicity in the range 0-0.0004 have three properties which favour higher BH masses as compared to higher metallicity models. These are (i) lower mass-loss rates during the post-MS phase, (ii) a more compact star disfavouring binary interaction and (iii) possible H-He shell interactions which lower the CO core mass. We conclude that it is possible that GW190521 may be the merger of black holes produced directly by massive stars from the first stellar generations. Our models indicate BH masses up to 70-75 Msun. Uncertainties related to convective mixing, mass loss, H-He shell interactions and pair-instability pulsations may increase this limit to ~85 Msun.

Citation

Farrell, E., Groh, J. H., Hirschi, R., Murphy, L., Kaiser, E., Ekström, S., …Meynet, G. (2021). Is GW190521 the merger of black holes from the first stellar generations?. Monthly Notices of the Royal Astronomical Society, 502(1), L40-L44. https://doi.org/10.1093/mnrasl/slaa196

Journal Article Type Article
Acceptance Date Dec 1, 2020
Online Publication Date Dec 20, 2020
Publication Date 2021-03
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 502
Issue 1
Pages L40-L44
DOI https://doi.org/10.1093/mnrasl/slaa196
Publisher URL http://dx.doi.org/10.1093/mnrasl/slaa196

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