Spin Evolution and Mass Distribution of Galactic Binary Neutron Stars
Binary neutron stars (BNSs) detected in the Milky Way have total masses distributing narrowly around ∼2.6–2.7 M _⊙ , while the BNS merger GW190425 detected via a gravitational wave has a significantly larger mass (∼3.4 M _⊙ ). This difference is not well understood, yet. In this paper, we investigat...
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2025-01-01
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| author | Qingbo Chu Youjun Lu Shenghua Yu |
| author_facet | Qingbo Chu Youjun Lu Shenghua Yu |
| author_sort | Qingbo Chu |
| collection | DOAJ |
| description | Binary neutron stars (BNSs) detected in the Milky Way have total masses distributing narrowly around ∼2.6–2.7 M _⊙ , while the BNS merger GW190425 detected via a gravitational wave has a significantly larger mass (∼3.4 M _⊙ ). This difference is not well understood, yet. In this paper, we investigate the BNS spin evolution via an improved binary star evolution model and its effects on the BNS observability, with the implementation of various relevant astrophysical processes. We find that the first-born neutron star component in low-mass BNSs can be spun up to millisecond pulsars by the accretion of Roche-lobe overflow from its companion and its radio lifetime can be comparable to the Hubble time. However, most high-mass BNSs have substantially shorter radio lifetimes than low-mass BNSs, and thus a smaller probability of being detected via radio emission. Adopting the star formation and metal enrichment history of the Milky Way given by observations, we obtain the survived Galactic BNSs with pulsar components from our population synthesis model and find that their distributions on the diagrams of the spin period versus the spin period time derivative ( $P-\dot{P}$ ) and the orbital period versus the eccentricity ( P _orb – e ) can well match those of the observed Galactic BNSs. The total mass distribution of the observed Galactic BNSs can also be matched by the model. A significant fraction (∼19%–22%) of merging BNSs at redshift z ∼ 0 have masses ≳3 M _⊙ , which seems compatible with the GW observations. Future radio observations may detect many more Galactic BNSs, which will put strong constraints on the spin evolution of BNSs during their formation processes. |
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| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-2c6ae01566854ab3b2ba43f7caa4b9f12025-08-20T02:12:46ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01980218110.3847/1538-4357/ad90e2Spin Evolution and Mass Distribution of Galactic Binary Neutron StarsQingbo Chu0Youjun Lu1https://orcid.org/0000-0002-1310-4664Shenghua Yu2National Astronomical Observatories, Chinese Academy of Sciences , 20A Datun Road, Beijing 100101, People’s Republic of China ; luyj@nao.cas.cn; School of Astronomy and Space Sciences, University of Chinese Academy of Sciences , 19A Yuquan Road, Beijing 100049, People’s Republic of ChinaNational Astronomical Observatories, Chinese Academy of Sciences , 20A Datun Road, Beijing 100101, People’s Republic of China ; luyj@nao.cas.cn; School of Astronomy and Space Sciences, University of Chinese Academy of Sciences , 19A Yuquan Road, Beijing 100049, People’s Republic of ChinaNational Astronomical Observatories, Chinese Academy of Sciences , 20A Datun Road, Beijing 100101, People’s Republic of China ; luyj@nao.cas.cnBinary neutron stars (BNSs) detected in the Milky Way have total masses distributing narrowly around ∼2.6–2.7 M _⊙ , while the BNS merger GW190425 detected via a gravitational wave has a significantly larger mass (∼3.4 M _⊙ ). This difference is not well understood, yet. In this paper, we investigate the BNS spin evolution via an improved binary star evolution model and its effects on the BNS observability, with the implementation of various relevant astrophysical processes. We find that the first-born neutron star component in low-mass BNSs can be spun up to millisecond pulsars by the accretion of Roche-lobe overflow from its companion and its radio lifetime can be comparable to the Hubble time. However, most high-mass BNSs have substantially shorter radio lifetimes than low-mass BNSs, and thus a smaller probability of being detected via radio emission. Adopting the star formation and metal enrichment history of the Milky Way given by observations, we obtain the survived Galactic BNSs with pulsar components from our population synthesis model and find that their distributions on the diagrams of the spin period versus the spin period time derivative ( $P-\dot{P}$ ) and the orbital period versus the eccentricity ( P _orb – e ) can well match those of the observed Galactic BNSs. The total mass distribution of the observed Galactic BNSs can also be matched by the model. A significant fraction (∼19%–22%) of merging BNSs at redshift z ∼ 0 have masses ≳3 M _⊙ , which seems compatible with the GW observations. Future radio observations may detect many more Galactic BNSs, which will put strong constraints on the spin evolution of BNSs during their formation processes.https://doi.org/10.3847/1538-4357/ad90e2AccretionCompact binary starsGravitational wave sourcesNeutron starsStellar evolutionX-ray binary stars |
| spellingShingle | Qingbo Chu Youjun Lu Shenghua Yu Spin Evolution and Mass Distribution of Galactic Binary Neutron Stars The Astrophysical Journal Accretion Compact binary stars Gravitational wave sources Neutron stars Stellar evolution X-ray binary stars |
| title | Spin Evolution and Mass Distribution of Galactic Binary Neutron Stars |
| title_full | Spin Evolution and Mass Distribution of Galactic Binary Neutron Stars |
| title_fullStr | Spin Evolution and Mass Distribution of Galactic Binary Neutron Stars |
| title_full_unstemmed | Spin Evolution and Mass Distribution of Galactic Binary Neutron Stars |
| title_short | Spin Evolution and Mass Distribution of Galactic Binary Neutron Stars |
| title_sort | spin evolution and mass distribution of galactic binary neutron stars |
| topic | Accretion Compact binary stars Gravitational wave sources Neutron stars Stellar evolution X-ray binary stars |
| url | https://doi.org/10.3847/1538-4357/ad90e2 |
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