论文标题
中子星合并中的延迟积聚：对短伽马射线爆发和基洛诺维的影响
Late-time accretion in neutron star mergers: implications for short gamma-ray bursts and kilonovae
论文作者
论文摘要
我们研究了中子恒星（NS）-NS或NS-Black孔合并后的积聚磁盘的长期（T >> 10 s）演变，并考虑了最初几秒钟内由R过程的放射性加热。我们发现，在合并后，累积加热最终超过了T〜10^2 s（α/0.1）^{ - 1.8}（m/2.6 msun）^{1.8}处的磁盘的结合能，其中shakura-sunyaev粘度参数是shakura-sunyaev粘度参数，m是余物对象的质量。这会导致磁盘迅速蒸发，并关闭喷气功率。我们建议这是在许多短伽马射线爆发（GRB）中看到的延长发射（EE）或X射线高原末端急剧下降的原因。在急剧下降之前的浅磁通演变与合理的情况一致，其中射流功率与磁盘质量线性缩放。我们建议来自NS合并的喷气机具有两个组成部分 - 一个短呈狭窄的狭窄，与迅速的伽马射线发射和产生EE的持久宽分量相对应。这导致了一个预测，“孤儿EE”（没有及时的伽马射线）可能是通过未来宽场X射线调查可观察到的NS合并的有希望的电磁对应物。长寿命的磁盘会产生缓慢的弹射分量，可以有效地将Beta-Decay电子携带的能量高达t〜100 d，并在这些晚期时代占基洛诺瓦辐射光度的10％。我们预测，附近（<100 MPC）NS合并的未来基于地面和JWST近IR光谱将在合并后的几周内检测到狭窄（〜0.01c）线的特征，这提供了这些事件中形成的原子种类的有力探测。
We study the long-term (t >> 10 s) evolution of the accretion disk after a neutron star(NS)-NS or NS-black hole merger, taking into account the radioactive heating by r-process nuclei formed in the first few seconds. We find that the cumulative heating eventually exceeds the disk's binding energy at t ~ 10^2 s (α/0.1)^{-1.8} (M/2.6 Msun)^{1.8} after the merger, where αis the Shakura-Sunyaev viscosity parameter and M is the mass of the remnant object. This causes the disk to evaporate rapidly and the jet power to shut off. We propose that this is the cause of the steep flux decline at the end of the extended emission (EE) or X-ray plateau seen in many short gamma-ray bursts (GRBs). The shallow flux evolution before the steep decline is consistent with a plausible scenario where the jet power scales linearly with the disk mass. We suggest that the jets from NS mergers have two components -- a short-duration narrow one corresponding to the prompt gamma-ray emission and a long-lasting wide component producing the EE. This leads to a prediction that "orphan EE" (without the prompt gamma-rays) may be a promising electromagnetic counterpart for NS mergers observable by future wide-field X-ray surveys. The long-lived disk produces a slow ejecta component that can efficiently thermalize the energy carried by beta-decay electrons up to t ~ 100 d and contributes 10% of the kilonova's bolometric luminosity at these late epochs. We predict that future ground-based and JWST near-IR spectroscopy of nearby (< 100 Mpc) NS mergers will detect narrow (~0.01c) line features a few weeks after the merger, which provides a powerful probe of the atomic species formed in these events.
