Improving and Extending Models of Gamma-Ray Burst Afterglows

改进和扩展伽马射线暴余辉模型

• 批准号: 1716567
• 负责人: Lorenzo Sironi
• 金额: $ 45.78万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1716567&HistoricalAwards=false
• 关键词: Improving; Extending; Models; Gamma; Ray

Gamma-ray bursts (GRBs) are the most luminous cosmic explosions. They are some of the more extreme objects in the Universe, both mysterious and fascinating. Understanding their origin and development provides insights into star formation and evolution, as well as tests of basic physics. The afterglow left after a GRB goes off is due to interactions in the material around the explosion and can be observed long after the initial blast. This project will probe the afterglow phase in new ways using extensive computer simulations to go beyond the simple models and explain otherwise puzzling recent observations.Because of the way the spectrum of the afterglow changes with time, the dominant emission mechanism was thought to be synchrotron radiation from shock-accelerated electrons. However, the detection of photons with energies that violate the maximum synchrotron limit shows that theoretical understanding of the afterglow emission is still incomplete. Current models have little predictive power due to ignorance of the underlying microphysics. This work will go beyond standard phenomenological approaches, building on recent results by this research team that have started to unveil the microphysics of GRB afterglows. Self-consistent particle-in-cell simulations will provide physically grounded microphysical parameters at every stage. This study will (1) settle the question of the origin of the magnetization; (2) study the shock physics in early GRB afterglows, investigating the electron-positron-proton plasma shocks; and (3) explore the shock physics in late GRB afterglows. The research will assess the efficiencies of electron and proton acceleration in late GRB shocks, and the decay length of the generated and amplified fields.Despite the complex physics involved, this work contains several projects for undergraduate students, and even high school students can be exposed to the latest developments about relativistic shocks through day-long workshops. The team is committed to significant involvement with established educational and mentorship programs, including support for children and adolescents from disadvantaged neighborhoods.

伽玛射线暴（GRB）是最明亮的宇宙爆炸。 它们是宇宙中一些更极端的物体，既神秘又迷人。 了解它们的起源和发展提供了对星星形成和演化的见解，以及对基本物理学的测试。 伽玛射线暴爆炸后留下的余辉是由于爆炸周围物质的相互作用，并且可以在最初爆炸后很长时间内观察到。 该项目将使用广泛的计算机模拟以新的方式探索余辉阶段，超越简单的模型，并解释最近令人困惑的观测结果。由于余辉光谱随时间变化的方式，主要的发射机制被认为是来自冲击加速电子的同步辐射。 然而，探测到的光子的能量违反了最大同步辐射极限表明，理论上的理解余辉发射仍然是不完整的。 目前的模型几乎没有预测能力，由于忽略了潜在的微观物理。 这项工作将超越标准的现象学方法，建立在这个研究小组最近的成果之上，这些成果已经开始揭示GRB余辉的微观物理学。 自洽的粒子模拟将在每个阶段提供物理基础的微物理参数。 本研究将（1）解决磁化的起源问题;（2）研究早期GRB余辉中的激波物理，研究电子-正电子-质子等离子体激波;（3）探索晚期GRB余辉中的激波物理。 这项研究将评估伽玛射线暴后期冲击中电子和质子加速的效率，以及产生和放大的场的衰减长度。尽管涉及复杂的物理学，这项工作包括几个面向本科生的项目，甚至高中生也可以通过为期一天的研讨会接触到相对论冲击的最新发展。 该团队致力于积极参与既定的教育和辅导计划，包括为弱势社区的儿童和青少年提供支持。

项目成果

Two Years of Nonthermal Emission from the Binary Neutron Star Merger GW170817: Rapid Fading of the Jet Afterglow and First Constraints on the Kilonova Fastest Ejecta

• DOI: 10.3847/2041-8213/ab5226
• 发表时间: 2019-09
• 期刊: The Astrophysical Journal Letters
• 作者: A. Hajela;R. Margutti;K. Alexander;A. Kathirgamaraju;A. Kathirgamaraju;A. Baldeschi;C. Guidorzi;D. Giannios;W. Fong;Y. Wu;A. MacFadyen;A. Paggi;E. Berger;P. Blanchard;R. Chornock;D. Coppejans;P. Cowperthwaite;T. Eftekhari;S. Gomez;G. Hosseinzadeh;T. Laskar;B. Metzger;M. Nicholl;M. Nicholl;K. Paterson;D. Radice;L. Sironi;G. Terreran;V. Villar;P. G. Williams;P. G. Williams;Xiaoyi Xie;J. Zrake

Stochastic Ion Acceleration by the Ion-cyclotron Instability in a Growing Magnetic Field

不断增长的磁场中离子回旋加速器不稳定性导致的随机离子加速

• DOI: 10.3847/1538-4357/ab2592
• 发表时间: 2019
• 期刊: The Astrophysical Journal
• 作者: Ley, Francisco;Riquelme, Mario;Sironi, Lorenzo;Verscharen, Daniel;Sandoval, Astor
• 通讯作者: Sandoval, Astor

The Binary Neutron Star Event LIGO/Virgo GW170817 160 Days after Merger: Synchrotron Emission across the Electromagnetic Spectrum

• DOI: 10.3847/2041-8213/aab2ad
• 发表时间: 2018-01
• 期刊: The Astrophysical Journal Letters
• 作者: R. Margutti;K. Alexander;Xiaoyi Xie;L. Sironi;B. Metzger;A. Kathirgamaraju;W. Fong;P. Blanchard;E. Berger;A. MacFadyen;D. Giannios;C. Guidorzi;A. Hajela;R. Chornock;P. Cowperthwaite;T. Eftekhari;M. Nicholl;V. Villar;P. G. Williams;J. Zrake

Electron Heating in Low Mach Number Perpendicular Shocks. II. Dependence on the Pre-shock Conditions

• DOI: 10.3847/1538-4357/aab6ad
• 发表时间: 2017-12
• 期刊: The Astrophysical Journal
• 作者: Xinyi Guo;L. Sironi;R. Narayan

Electron Heating in Low-Mach-number Perpendicular Shocks. I. Heating Mechanism

• DOI: 10.3847/1538-4357/aa9b82
• 发表时间: 2017-10
• 期刊: The Astrophysical Journal
• 作者: Xinyi Guo;L. Sironi;R. Narayan