Black hole–neutron star and binary neutron star mergers from Population III and II stars

Population III (Pop. III) stars are expected to be massive and to undergo minimal mass loss due to their lack of metals, making them ideal progenitors of black holes and neutron stars. Here, we investigate the formation and properties of binary neutron star (BNS) and black hole-neutron star (BHNS) mergers originating from Pop. III stars, and compare them to their metal-enriched Population II (Pop. II) counterparts, focusing on their merger rate densities (MRDs), primary masses, and delay times. We find that, despite the high merger efficiency of Pop. III BNSs and BHNSs, their low star formation rate results in a MRD at least one order of magnitude lower than that of Pop. II stars. The MRD of Pop. III BNSs peaks at redshift z ~ 15, attaining a value R BNS ( z ~ 15) ~ 15 Gpc −3 yr −1 , while the MRD of Pop. III BHNSs is maximum at z ~ 13, reaching a value of R BHNS ( z ~ 13) ~ 2Gpc −3 yr −1 . Finally, we observe that the black hole masses of Pop. III BHNS mergers have a nearly flat distribution, with a peak at ∼20 M ⊙ and extending up to ∼50 M ⊙ . Black holes in Pop. II BHNS mergers instead show a peak at ≲ 15 M ⊙ . We consider these predictions in light of recent gravitational-wave observations in the local Universe, finding that a Pop. III origin is preferred relative to Pop. II for some events.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-10-28
DOI
https://doi.org/10.1051/0004-6361/202555951
Primary Topic
Pulsars and Gravitational Waves Research
Type
article
Field-Weighted Citation Impact
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article

Black hole–neutron star and binary neutron star mergers from Population III and II stars

Matthew Mould, Boyuan Liu, Manuel Arca Sedda, Veronika Lipatova et al.
Astronomy and Astrophysics
Pulsars and Gravitational Waves Research
article

Black hole–neutron star and binary neutron star mergers from Population III and II stars

Matthew Mould, Boyuan Liu, Manuel Arca Sedda, Veronika Lipatova, M. Branchesi, Filippo Santoliquido, Guglielmo Costa, Ralf S. Klessen, Michela Mapelli, Benedetta Mestichelli, Lavinia Paiella, Giuliano Iorio
article en

Abstract

Population III (Pop. III) stars are expected to be massive and to undergo minimal mass loss due to their lack of metals, making them ideal progenitors of black holes and neutron stars. Here, we investigate the formation and properties of binary neutron star (BNS) and black hole-neutron star (BHNS) mergers originating from Pop. III stars, and compare them to their metal-enriched Population II (Pop. II) counterparts, focusing on their merger rate densities (MRDs), primary masses, and delay times. We find that, despite the high merger efficiency of Pop. III BNSs and BHNSs, their low star formation rate results in a MRD at least one order of magnitude lower than that of Pop. II stars. The MRD of Pop. III BNSs peaks at redshift z ~ 15, attaining a value R BNS ( z ~ 15) ~ 15 Gpc −3 yr −1 , while the MRD of Pop. III BHNSs is maximum at z ~ 13, reaching a value of R BHNS ( z ~ 13) ~ 2Gpc −3 yr −1 . Finally, we observe that the black hole masses of Pop. III BHNS mergers have a nearly flat distribution, with a peak at ∼20 M ⊙ and extending up to ∼50 M ⊙ . Black holes in Pop. II BHNS mergers instead show a peak at ≲ 15 M ⊙ . We consider these predictions in light of recent gravitational-wave observations in the local Universe, finding that a Pop. III origin is preferred relative to Pop. II for some events.

Astronomy and AstrophysicsVol. 704
Heidelberg University (DE), Istituto Nazionale di Fisica Nucleare, Galileo Galilei Institute for Theoretical Physics (IT), LIGO Scientific Collaboration (US), Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Gran Sasso (IT), Kavli Institute for Particle Astrophysics and Cosmology (US), Institut Català de Ciències del Clima (ES), Istituto Nazionale di Fisica Nucleare, Sezione di Padova (IT), Center for Southeast Asian Studies (FR), Forschungsstätte der Evangelischen Studiengemeinschaft (DE), Center for Astrophysics Harvard & Smithsonian (US), Collurania Teramo Observatory (IT), Gran Sasso Science Institute (IT), Osservatorio Astronomico di Padova (IT), Massachusetts Institute of Technology (US)
Openalex Percentile: Top 78%
Pulsars and Gravitational Waves Research
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