双中子星并合中单个中子星自旋对抛射物、r-过程核合成及千新星的印记
The imprint of individual neutron star spins on ejecta, $r$-process nucleosynthesis, and kilonovae in binary neutron star mergers
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中文总结 AI 辅助
本文研究双中子星并合中单个自旋对抛射物、r-过程核合成及千新星的效应，发现其可通过电磁信号打破引力波中自旋简并，对千新星观测有重要意义。
中文摘要 AI 辅助
引力波（GW）信号中，双中子星的单个自旋χ₁和χ₂仅通过有效自旋参数χ_eff产生主导阶影响。本文首次系统研究单个自旋对抛射物、r-过程核合成及千新星辐射的效应，在固定总质量、质量比和χ_eff的条件下开展对比分析。研究采用数值相对论方法获取三个总质量区间的抛射物，结合与温度、成分相关的SFHo物态方程及中微子发射与吸收过程。对于总质量M_tot=2.55M⊙且固定χ_eff=0的情况，单个自旋使动力学抛射物质量变化约45倍，A≥140的绝对产额跨度超两个数量级，镧系元素与轻r-过程元素的质量比从约2升至约70； prompt坍缩的4.10M⊙模型在χ_eff=0时，重元素产额差异超四个数量级。千新星保留单个自旋的印记，峰值亮度差异达约0.9星等；在40Mpc处，所有三对固定χ_eff=0的系统在常用观测时刻的亮度均高于采用的探测深度，同时刻色指数差异达约1.5星等。当用相同参数化吸积盘外流替代模拟得到的长期抛射物时，色指数印记仍存在，说明吸积盘质量差异并非主要驱动因素，动力学抛射物贡献重要；中微子吸收会系统性增亮千新星并使峰值相关颜色蓝移。这些电磁信号可打破引力波信号中单个自旋的简并性。
英文摘要
To leading order, the gravitational-wave (GW) signal from binary neutron stars depends on the individual spins, $χ_1$ and $χ_2$, only through the effective spin parameter $χ_{\rm eff}$. We present the first systematic investigation of individual-spin effects on ejecta, $r$-process nucleosynthesis, and kilonova emission, including comparisons at fixed total mass, mass ratio and $χ_{\rm eff}$. We use numerical relativity ejecta from three total mass regimes with the finite-temperature, composition-dependent SFHo equation of state and neutrino emission and absorption. For $M_{\rm tot}=2.55\,M_\odot$ at fixed $χ_{\rm eff}=0$, individual spins change the dynamical ejecta mass by a factor of ${\sim}45$, while the absolute $A\geq140$ yield spans more than two orders of magnitude and the lanthanide to light $r$-process mass ratio increases from ${\sim}2$ to ${\sim}70$. Prompt-collapse $4.10\,M_\odot$ models show heavy-element yield differences exceeding four orders of magnitude at $χ_{\rm eff}=0$. The kilonova retains the individual-spin imprint, with peak brightness differences reaching ${\sim}0.9$ mag. At $40\,{\rm Mpc}$, all three fixed $χ_{\rm eff}=0$ pairs remain above adopted depths at common epochs for all viewing angles, with same-epoch colour differences reaching ${\sim}1.5$ mag. The colour imprint persists when the simulation-derived secular ejecta are replaced by the same parametric disc outflow, indicating that disc mass differences are not the primary driver and that dynamical ejecta make an important contribution. Neutrino absorption systematically brightens the kilonova and shifts peak-associated colours blueward. These EM signatures can break the degeneracy between individual spins in the GW signal.
