Collaborative Research: WoU-MMA: Coherent radio and x-ray precursor transients to gravitational wave events: Simulations in general relativity and kinetic theory

当今天体物理学的一个中心问题是理解中子星(NS)、高度致密天体或中子星与黑洞(BH)的合并。这种合并产生了引力波(GW)，一种对应的电磁信号，最终产生了宇宙中最重的原子元素。除了在这类系统合并期间和之后产生的对应物之外，由于在激励的NS中存在强磁场，还可能在碰撞前产生瞬时事件。这样的前兆事件最近被报道用于长伽马射线暴GRB 211211A。了解是否以及如何发射这样的瞬变将是至关重要的，因为它是通过帮助后续搜索GW余辉而迅速定位天空的额外工具，以及约束目前无法获取的参数，如合并前系统中的磁场强度。加州理工学院和马里兰大学帕克分校之间的一项研究合作，将通过广义相对论和动力学理论的计算机模拟程序来研究这些问题。该项目将为本科生和研究生提供培训，并包括在计算相对论和等离子体天体物理学的交叉点设立暑期班。研究人员将对地壳破碎机制进行首次数值模拟，这是产生前兆的主要假说。为了揭示系统中的实际发射机制，他们将在适用于致密天体合并和磁星的磁层的情况下，计算与相对论磁重联中的等离子体群合并相关的相干发射机制的效率。最后，他们将探索在强磁场中重新连接的一种新的辐射机制，并计算逃逸高能X射线光子的光谱。研究小组提供的结果(包括系统参数的预测频率范围和光度定标)和模拟代码将与NS-NS和NS-BH合并的多信使观测直接相关。这个暑期班计划将填补早期职业科学家培训机会的空白，为他们在相对论和多信使天体物理学领域的研究前沿做好准备。此外，该项目支持的博士后学者和研究生将接受广泛的专业、教育和公平、多样性和包容性培训，包括通过该项目的工作获得的可转移技能。这将使他们能够在整个职业生涯中处于有利地位，为科学和工程其他领域的技术进步和发现做出贡献。这一奖项推进了宇宙之窗大理想的目标。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

A central issue in astrophysics today is understanding the merging of neutron stars (NS), highly compact celestial objects, or NS with black holes (BH). Such mergers produce gravitational waves (GW), a counterpart electromagnetic signal, and ultimately the heaviest atomic elements in the universe. In addition to counterparts produced during and after the merger of such systems, it might also be possible to create prompt transient events before the collision, due to the presence of strong magnetic fields in the inspiraling NS. Such a precursor event was recently reported for the long gamma-ray burst GRB 211211A. Understanding whether and how such transients can be launched will be crucial both as an additional tool for prompt sky localization by aiding follow-up searches for GW afterglows, as well as constraining currently inaccessible parameters such as the magnetic field strengths in the pre-merger system. A research collaboration between California Institute of Technology and the University of Maryland, College Park, will investigate these issues through a program of computer simulations in general relativity and kinetic theory. The project will provide training for undergraduate and graduate students and include the creation of a summer school at the intersection of computational relativity and plasma astrophysics. The researchers will perform the first numerical simulations of the crustal shattering mechanism, which is the leading hypothesis for the production of a precursor. To uncover the actual emission mechanism in the system, they will calculate the efficiency of coherent emission mechanisms associated with mergers of plasmoids in relativistic magnetic reconnection, in regimes applicable to the magnetospheres of compact object mergers and magnetars. Finally, they will explore a novel radiative regime of reconnection in strong magnetic fields and calculate the spectrum of escaping high-energy X-ray photons. The results (including predicted frequency ranges and luminosity scalings with system parameters) and simulation codes provided by the research team will be directly relevant for multi-messenger observations of NS-NS and NS-BH mergers. This summer school program will fill a gap in the training opportunities of early career scientists, preparing them for research forefront of relativistic and multi-messenger astrophysics. In addition, postdoctoral scholars and graduate students supported by this project will receive extensive professional, educational, and equity, diversity, and inclusion training, including transferable skills acquired through work on this project. This will enable them to be well-positioned throughout their careers to contribute also to technical advances and discoveries in other areas of science and engineering. This award advances the goals of the 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.