Implications of Low Neutron Star Merger Rates for Gamma-Ray Bursts, r-process Production, and Galactic Double Neutron Stars
低中子星并合率对伽马射线暴、r-过程产生和银河系双中子星的启示
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 r-process elements. The initial merger rate from this single event 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 downward with recent gravitational-wave (GW) catalog updates. Analyzing GWTC-4, we find a total BNS merger rate of 28─300 Gpc<SUP>−3</SUP> yr<SUP>−1</SUP> consisting of <inline-formula> <mml:math><mml:mn>5</mml:mn><mml:msubsup><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>49</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>176</mml:mn></mml:mrow></mml:msubsup><mml:mspace></mml:mspace><mml:msup><mml:mrow><mml:mi>Gpc</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>3</mml:mn></mml:mrow></mml:msup><mml:mspace></mml:mspace><mml:msup><mml:mrow><mml:mi>yr</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:math> </inline-formula> in GW170817-like ∼ (1.3, 1.3) M<SUB>⊙</SUB> BNSs (90% credibility). 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) merger rate. Comparing to a BNS merger rate of 100 Gpc<SUP>−3</SUP> yr<SUP>−1</SUP>, the cosmological SGRB rate is a factor of 3.6─18 higher (despite kilonova followup of SGRBs implying a significant fraction of SGRBs are of BNS origin), the r-process rate is a factor of 0.9─4.1 higher (even though we consider only r-process elements above the second peak), 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.
展开 ▾采用分质量箱率估计减少质量分布外推不确定性,将 BNS、低质量 NSBH、SGRB、r-process 与银河 DNS 置于同一比较框架,并量化喷流开角、自旋、延迟时间分布等假设对率张力的影响。
自 GW170817 将 BNS 并合与短伽马暴、千新星证认后,GWTC-1/3 的较高并合率曾使引力波率与多信使探针大致相容 Mandel+ 2022。本文基于 GWTC-4 重新推断的总 BNS 率为 28–300 Gpc^-3 yr^-1,其中 GW170817 型低质量 BNS 为 53^{+176}_{-49} Gpc^-3 yr^-1;而宇宙学短伽马暴率(Rouco Escorial+ 2023)约为其 3.6–18 倍,暗示 BNS 至多只贡献少部分 SGRB。为解释银河重 r-process 质量所需并合率为 89–410 Gpc^-3 yr^-1,也与低 BNS 率要求更陡的延迟时间分布或更高喷出物产额 Kobayashi+ 2023;银河 DNS 反推率 32^{+19}_{-9} Myr^-1 Grunthal+ 2021 同样超过 GW 总率。未来随 O4 完整数据发布和探测器灵敏度提升,若 BNS 持续稀缺,多探针率比较将进一步约束喷流开角、星族历史与核合成通道,并可能指向非并合 SGRB/ r-process 来源。
预印本 2026-04-06 · 接收 2026-07-05 · 刊出 2026-07-27 · 收录 2026-08-20