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Energizing Photospheres of Gamma-Ray Bursts

伽马射线爆发的光球层能量

基本信息

批准号：
1816484
负责人：
Andrei Beloborodov
金额：
$ 62.21万
依托单位：
Columbia University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-08-01 至 2023-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1816484&HistoricalAwards=false
关键词：
Energizing Photospheres Gamma Ray Bursts

项目摘要

The detection of a gravitational wave event from a neutron star merger, GW 170817, coincident with a gamma-ray burst, GRB 170817A, is a major achievement of modern astrophysics. GRBs are the most extreme explosions in the Universe and GRB research can impact fundamental physics through understanding new properties of matter under extreme conditions. In order to better understand GRB 170817A and other GRBs, a research group at Columbia University will investigate how the GRB photosphere, or outer shell from which light is radiated, is energized to become so bright. This will be accomplished using state-of-the-art numerical tools developed by the group. The simulations of shock waves in the GRB, derived from first principles, will self-consistently include the creation of electron-positron (anti-electron) pairs, and predict the spectrum of the radiation produced, which can be compared with observations. The results will be used to develop a concrete physical scenario for GRB 170817A. The group will continue with its outreach activities through both public lectures and communications with the press, and the results will be disseminated at international conferences, colloquia, and seminars. Methods and results of the research will be taught as part of astrophysics courses at Columbia University, and the project will involve training of a postdoctoral scholar and students.Photospheric emission from opaque relativistic ejecta plays a key role in cosmological gamma-ray bursts. A key physics question is why the photosphere is so bright in GRBs and what processes shape its observed nonthermal spectrum. The proposed research will focus on building physical models for two heating mechanisms: (1) internal radiation-mediated shocks and (2) damping of a turbulent cascade. An important goal is to investigate how shocks break out at the photosphere, releasing their radiation. The code will directly follow the evolution of sub-photospheric shocks, coupled with propagation of individual photons around it, and calculate their breakout, accompanied by copious electron-positron pair creation. This method is particularly applicable to studies of gamma-ray counterparts of neutron star mergers. It can give a robust physical model for GRB 170817A and lead to specific predictions for counterparts of future gravitational wave detections. The results will have applications to short and long cosmological GRBs as well as shock breakout in supernova explosions. The planned research also includes a novel physical model for turbulence damping in GRB jets and the radiative effects of free neutrons.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.

探测到与伽马射线暴GRB 170817A重合的中子星合并GW 170817产生的引力波事件是现代天体物理学的一项重大成就。伽玛暴是宇宙中最极端的爆炸，伽玛暴研究可以通过了解极端条件下物质的新性质来影响基础物理。为了更好地理解伽玛暴170817A和其他伽玛暴，哥伦比亚大学的一个研究小组将研究伽玛暴光球，即辐射光线的外壳，是如何被激发到如此明亮的。这将使用该小组开发的最先进的数字工具来完成。对伽玛暴中冲击波的模拟源自第一原理，它将自始至终包括电子-正电子(反电子)对的产生，并预测所产生的辐射的光谱，这可以与观测结果进行比较。结果将被用来为GRB 170817A制定一个具体的物理场景。该小组将通过公开讲座和与新闻界的交流继续其外联活动，并将在国际会议、座谈会和研讨会上传播其成果。这项研究的方法和结果将作为哥伦比亚大学天体物理学课程的一部分教授，该项目将包括对博士后学者和学生的培训。不透明的相对论抛射物的光层发射在宇宙学伽马射线爆发中起着关键作用。一个关键的物理问题是，为什么伽玛暴的光球如此明亮，是什么过程塑造了它的观测到的非热谱。拟议的研究将集中于建立两种加热机制的物理模型：(1)内辐射诱导的激波和(2)湍流叶栅的衰减。一个重要的目标是研究激波如何在光球层爆发，释放出它们的辐射。该代码将直接跟踪亚光球冲击的演变，以及它周围单个光子的传播，并计算它们的突破，同时产生大量的电子-正电子对。这种方法特别适用于中子星合并的伽马射线对应物的研究。它可以为GRB 170817A提供一个稳健的物理模型，并导致对未来引力波探测的对应物的具体预测。这些结果将应用于短的和长的宇宙学伽玛暴以及超新星爆炸中的激波爆发。计划中的研究还包括一种新的物理模型，用于研究伽玛暴喷流中的湍流衰减和自由中子的辐射效应。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。