Collaborative research: WoU-MMA: Electrodynamics of Magnetospheric Interactions in Merging Neutron Star Binaries

2017年8月探测到两颗中子星合并产生的引力波是天体物理学的重大事件。这两颗密度极高的前恒星的合并与一次短伽马射线暴（GRB）有关，这清楚地表明，合并为这种异常明亮的天体物理爆炸的短时间类提供了中心引擎。为了更好地理解中子星合并是如何产生短伽马射线暴的，普渡大学和普林斯顿大学之间的一项研究合作将对合并进行理论和数值研究，特别关注合并中最早可能产生的电磁辐射，即中子星在主事件发生前相互旋转时产生的前体光。研究人员将对合并中子星的相互作用磁场进行模拟，估计从可能的相干无线电波到x射线的功率、角度模式和宽带发射机制。该项目结合了高能天体物理学和等离子体物理学的广泛领域的研究。该项目解决了与引力波天文学、超强磁场相互作用和亚原子粒子加速有关的多信使天体物理学中的各种问题。调查结果也将有助于制定寻找可能的合并前体发射的战略。这项研究将包括两所大学的本科生的参与，以及一个扩展项目，包括正在研究的互动的动画电影。最有可能产生前体发射的情况是两颗中子星的电磁相互作用，通过在共同中子星磁层内磁化等离子体的相对运动产生感应电场。据估计，在第二颗中子星形成后至少数百万年的合并时间足够长，以至于在合并时，每个磁层可能都是自己死亡的。随着恒星的旋转，磁层可以因相对轨道运动而恢复。该项目的主要目标是通过采用脉冲星磁层范式来研究普通磁层的轨道复兴：由于磁化等离子体的运动和随后的真空击穿而产生的感应电场。研究人员将考虑间隙的形成：沿磁场线具有高电场的区域，以及相互作用中子星的轨道调制共同磁层中的重联层。中子星的自旋和轨道运动可能在共同磁层内产生有利于发电机作用的条件，这将放大磁场。该团队还将研究通过生产等离子体微波激射器产生高亮度相干射电辐射。这个项目推进了NSF宇宙大构想窗口的目标。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The detection of gravitational waves from the merger of two neutron stars in August 2017 was a seminal event for astrophysics. This amalgamation of two extremely dense former stars was associated with a short gamma-ray burst (GRB), making it clear that a merger provides the central engine of the short-duration class of this extraordinarily bright type of astrophysical explosion. In order to better understand how a neutron star merger produces a short GRB, a research collaboration between Purdue University and Princeton University will carry out theoretical and numerical investigations of the merger, with a particular focus on the earliest possible electromagnetic radiation from the merger, the precursor light produced as the neutron stars spiral toward each other before the main event. The researchers will perform simulations of the interacting magnetic fields of merging neutron stars, estimating the power, angular pattern and broadband emission mechanisms, from possible coherent radio waves to X-rays. The project combines research in broad areas of high energy astrophysics and plasma physics. The project addresses diverse problems in multi-messenger astrophysics related to gravitational wave astronomy, interaction of ultra-strong magnetic fields and acceleration of sub-atomic particles. The results of the investigation will also help formulate the strategies for searching for possible merger precursor emission. The research will include involvement of undergraduate students at both universities and an outreach program including animated movies of the interactions being studied.The most likely scenario to generate precursor emission is the electromagnetic interaction of two neutron stars via the creation of inductive electric fields through the relative motion of magnetized plasma within the common neutron star magnetosphere. It is expected that merger times, at least millions of years after the formation of the second neutron star, are sufficiently long that, at the time of the merger, each magnetosphere is likely to be dead on its own. As the stars spiral in, the magnetospheres can be revived due to the relative orbital motion. The main goal of the project is to study this orbital revival of the common magnetospheres by employing the pulsar magnetosphere paradigm: the generation of the inductive electric field due to the motion of magnetized plasma and ensuing vacuum breakdown. The researchers will consider the formation of gaps: regions with high electric field along magnetic field lines, and reconnection layers in the orbital-modulated common magnetosphere of interacting neutron stars. Spins and orbital motion of the neutron stars may generate conditions favorable for dynamo action within the common magnetosphere, which will amplify the magnetic field. The team will also study the generation of high brightness coherent radio emission via the production of a plasma maser. This project advances the goals of the NSF Windows on the Universe Big Idea.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.