AI 中文总结
研究利用二维构型量化中子星合并抛射物结构对谱线形状影响，考虑硒、碲、钨元素，展示多种轮廓形状，发现线形状对抛射物结构敏感，可据此限制观测角或合并属性，如二元质量比、高密度物质状态方程
AI 中文摘要
数值模拟表明中子星合并喷射出具有复杂、非球形密度和成分分布的物质。本文利用长期流体动力学模拟得到的合并抛射物的二维构型，来量化这种抛射物结构在光学薄极限下对谱线形状的影响。考虑了千新星建模中感兴趣的三个元素（硒、碲和钨），并展示了模型样本和观测者方向的轮廓形状。许多计算得出复杂的轮廓形状。对于硒和碲，晚期轮廓形状对合并后从遗迹黑洞环面系统发射的低速抛射物（约0.1c）的结构最敏感，而对于较重元素，合并后立即发射的更快膨胀和更富中子的动力学抛射物的贡献更显著，导致更宽的线形状。还发现r过程元素衰变引起的加热的动力学影响会导致比忽略此效应的模型所暗示的更宽的峰值。虽然理想化，但计算表明线形状对抛射物结构敏感，因此可以限制极观测角或合并的潜在属性，这些属性决定了抛射物成分中元素的空间分布，如二元质量比甚至高密度物质的状态方程。
英文摘要
Numerical simulations suggest that neutron star mergers eject material with complex, non-spherical density and composition distributions. Here we use two-dimensional configurations of merger ejecta obtained from long-term hydrodynamic simulations to quantify the influence of such ejecta structure on the shapes of spectral lines in the optically thin limit. We consider three example elements of interest for kilonova modelling (selenium, tellurium and tungsten) and illustrate profile shapes for a sample of models and observer orientations. Many of our calculations yield complex profile shapes, including cases with multiple peaks and/or extended wings on scales large enough to be relevant to interpreting observations. For selenium and tellurium, our late-phase profile shapes are most sensitive to the structure of the low-velocity ejecta (~0.1c) launched after the merger from the relic black-hole torus system, while for heavier elements the contribution from the more rapidly expanding and more neutron-rich dynamical ejecta launched right after the merger is more significant and leads to broader line shapes. We also find that the dynamical influence of heating due to the decay of r-process elements can lead to considerably broader peaks than suggested by models that neglect this effect. Although idealised, our calculations demonstrate that line shapes are sensitive to the ejecta structure and could therefore constrain the polar observation angle or underlying properties of the merger that determine the spatial distributions of elements in the ejecta components, such as the binary mass ratio or even the equation of state of high-density matter.
Comments16 pages, 10 figures, submitted to MNRAS
