Implications of low neutron star merger rates for gamma-ray bursts, r-process production and Galactic double neutron stars
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| Format: | Preprint |
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2026
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| _version_ | 1866918430556291072 |
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| author | Fishbach, Maya Ji, Alexander P. Fong, Wen-fai Wu, Tom Y. Rastinejad, Jillian C. Vijaykumar, Aditya Chen, Hsin-Yu |
| author_facet | Fishbach, Maya Ji, Alexander P. Fong, Wen-fai Wu, Tom Y. Rastinejad, Jillian C. Vijaykumar, Aditya Chen, Hsin-Yu |
| contents | The first multimessenger discovery of a binary neutron star (BNS) merger, GW170817, proved that such mergers can source short gamma-ray bursts (SGRBs) and produce \rprocess elements. The initial merger rate from this single event in the first two observing runs of the LIGO-Virgo observatory network, $110$--$3840\,\mathrm{Gpc}^{-3}\,\mathrm{yr}^{-1}$, was found to be broadly consistent with the SGRB rate, the Milky Way (MW) r-process mass, and the Galactic population of double neutron star (DNS) systems that will merge in a Hubble time. However, only one additional BNS merger has been detected since, and the BNS merger rate has been consistently revised downwards with the past few gravitational wave (GW) catalog updates. Analyzing GW data from the latest catalog GWTC-4, we find a total BNS merger rate of $28$--$300\,\mathrm{Gpc}^{-3}\,\mathrm{yr}^{-1}$ (consistent with the most recently published values from LIGO-Virgo-KAGRA) consisting of $53^{+176}_{-49}\,\mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$ in GW170817-like $\sim(1.3,1.3)\,M_\odot$ BNSs (90\% credibility). In light of this updated GW rate, we revisit the consistency of the BNS merger rate with SGRBs, r-process and Galactic DNSs. In all cases, there is an emerging tension with the BNS (and EM-bright neutron star--black hole, NSBH) merger rate. Comparing to a BNS merger rate of $100\,\mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$, the cosmological SGRB rate is a factor of 3.6--18 higher, the r-process rate is a factor of 0.9--4.1 higher, and the rate inferred from Galactic DNSs is a factor of 2.3--5.1 higher than the BNS rate. We discuss how various uncertainties in the inferred rates either alleviate or exacerbate this tension, which point to the various physical processes that can be constrained by such rate comparisons. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_05059 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Implications of low neutron star merger rates for gamma-ray bursts, r-process production and Galactic double neutron stars Fishbach, Maya Ji, Alexander P. Fong, Wen-fai Wu, Tom Y. Rastinejad, Jillian C. Vijaykumar, Aditya Chen, Hsin-Yu High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology The first multimessenger discovery of a binary neutron star (BNS) merger, GW170817, proved that such mergers can source short gamma-ray bursts (SGRBs) and produce \rprocess elements. The initial merger rate from this single event in the first two observing runs of the LIGO-Virgo observatory network, $110$--$3840\,\mathrm{Gpc}^{-3}\,\mathrm{yr}^{-1}$, was found to be broadly consistent with the SGRB rate, the Milky Way (MW) r-process mass, and the Galactic population of double neutron star (DNS) systems that will merge in a Hubble time. However, only one additional BNS merger has been detected since, and the BNS merger rate has been consistently revised downwards with the past few gravitational wave (GW) catalog updates. Analyzing GW data from the latest catalog GWTC-4, we find a total BNS merger rate of $28$--$300\,\mathrm{Gpc}^{-3}\,\mathrm{yr}^{-1}$ (consistent with the most recently published values from LIGO-Virgo-KAGRA) consisting of $53^{+176}_{-49}\,\mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$ in GW170817-like $\sim(1.3,1.3)\,M_\odot$ BNSs (90\% credibility). In light of this updated GW rate, we revisit the consistency of the BNS merger rate with SGRBs, r-process and Galactic DNSs. In all cases, there is an emerging tension with the BNS (and EM-bright neutron star--black hole, NSBH) merger rate. Comparing to a BNS merger rate of $100\,\mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$, the cosmological SGRB rate is a factor of 3.6--18 higher, the r-process rate is a factor of 0.9--4.1 higher, and the rate inferred from Galactic DNSs is a factor of 2.3--5.1 higher than the BNS rate. We discuss how various uncertainties in the inferred rates either alleviate or exacerbate this tension, which point to the various physical processes that can be constrained by such rate comparisons. |
| title | Implications of low neutron star merger rates for gamma-ray bursts, r-process production and Galactic double neutron stars |
| topic | High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2604.05059 |