Dynamical ejecta of neutron star mergers with nucleonic weak processes II: Kilonova emission
Dynamical ejecta of neutron star mergers with nucleonic weak processes II: Kilonova emission
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中子星并合与核子弱过程的动力学喷射物II：千新星发射
DOI：
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Mpa Garching
中科院分区：
文献类型：
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作者：
O. Just;I. Kullmann;S. Goriely;A. Bauswein;H. Janka;C. E. C. G. Darmstadt;Abbl Riken;Saitama;Ulb Brussels;Mpa Garching
中子星（NS）合并期间喷射物质的千新星（或宏新星）发射的大多数现有结果都是基于（准）单区模型或手动构建的玩具模型喷射物配置。在这项研究中，我们直接使用一般相对论平滑粒子流体动力学模拟的流出轨迹，对 NS 合并的第一个 ∼ 10 ms 期间喷射的物质（称为动态喷射物）进行了千新星分析，包括复杂的中微子处理和相应的核合成结果，这些结果已在本研究的第一部分中介绍。我们采用具有近似 M1 闭包的多维两矩辐射传输方案来演化光子场，并对通过基于原子物理学的参考结果进行校准而发现的不透明度使用启发式处方。我们发现光球层一般是椭球体，但有小尺度结构增强，并且产生的发射强度向极点方向比向赤道方向强约 1.5-3 倍。千新星通常在 0 后达到峰值。 7 − 1 。在近红外频率范围内持续 5 天，光度在 3 − 7 × 10 40 erg s − 1 之间，光球温度为 2 。 2 − 2 。 8 × 10 3 K。较软的状态方程或较高的二元质量不对称性会导致更长、更亮的信号。对于具有人工修改的电子分数的模型，还获得了光变曲线的显着变化，这强调了可靠的中微子输运模型的重要性。这里研究的模型仅考虑动态喷射物，没有一个模型能产生像 AT2017gfo 一样明亮的瞬态。我们模型的近红外峰值与 AT2017gfo 的早期蓝色成分不兼容。
The majority of existing results for the kilonova (or macronova) emission from material ejected during a neutron-star (NS) merger is based on (quasi-)one-zone models or manually constructed toy-model ejecta configurations. In this study we present a kilonova analysis of the material ejected during the first ∼ 10 ms of a NS merger, called dynamical ejecta, using directly the outflow trajectories from general relativistic smoothed-particle hydrodynamics simulations including a sophisticated neutrino treatment and the corresponding nucleosynthesis results, which have been presented in Part I of this study. We employ a multi-dimensional two-moment radiation transport scheme with approximate M1 closure to evolve the photon field and use a heuristic prescription for the opacities found by calibration with atomic-physics based reference results. We find that the photosphere is generically ellipsoidal but augmented with small-scale structure and produces emission that is about 1.5-3 times stronger towards the pole than the equator. The kilonova typically peaks after 0 . 7 − 1 . 5 days in the near-infrared frequency regime with luminosities between 3 − 7 × 10 40 erg s − 1 and at photospheric temperatures of 2 . 2 − 2 . 8 × 10 3 K. A softer equation of state or higher binary-mass asymmetry leads to a longer and brighter signal. Significant variations of the light curve are also obtained for models with artificially modified electron fractions, emphasizing the importance of a reliable neutrino-transport modeling. None of the models investigated here, which only consider dynamical ejecta, produces a transient as bright as AT2017gfo. The near-infrared peak of our models is incompatible with the early blue component of AT2017gfo.