Particle Acceleration at Relativistic Shocks: Implications for Models of Gamma-Ray Bursts and Active Galaxies

相对论冲击下的粒子加速：对伽马射线爆发和活动星系模型的影响

• 批准号: 0098705
• 负责人: Matthew Baring
• 金额: $ 21万
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-06-15 至 2006-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0098705&HistoricalAwards=false
• 关键词: Particle; Acceleration; Relativistic; Shocks; Implications

AST 0098705BaringGamma Ray Bursts (GRBs) are among the most fascinating objects known in the universe, possessing a uniqueness embodied in their ephemeral nature. Their discovery around 30 years ago has led to a sequence of baffling mysteries and startling revelations. The latest advance among these was the discovery in 1997 of fading X-ray, optical and radio afterglows that have permitted accurate determination of their distance from Earth, placing them in the most remote realms of the universe. Consequently, astrophysicists have arrived at the conclusion that GRBs are the most luminous and powerful objects in the universe. Current thinking is that they are spawned by a catastrophic event, perhaps an explosion of a massive star. The goals of this project are to investigate catastrophic event models of GRBs. In these models, the GRB occurs when the ejected material from the star ploughs into the surrounding ambient gas at highly supersonic and relativistic speeds, creating an enormously powerful cosmic shock wave. Energy is liberated, both in thermal forms and in the form of extremely relativistic elementary particles. These high-speed particles then produce radiative emission, which is detected on Earth as gamma rays, X-rays, radio waves and optical light. The uncertainties in this dissipative shock scenario essentially stem from two constraints: (i) the relatively short duration and narrow energy bandwidth of the prompt gama-ray data, and (ii) the present crudeness of theoretical models. This project addresses these limitations. It explores how the relativistic particles can obtain the necessary extreme energies. It includes much more accurate determinations than previously available of the maximum energies attainable. It also seeks to establish definitive correlations and trends between particle acceleration properties and the radiation we see, using the latter as a diagnostic probe on the acceleration physics. The big questions this work seeks to answer include (i) whether the GRB environment is an ordered large scale phenomenon, or whether it possesses a multitude of chaotic, entangled, magnetized cells, (ii) if both of these situations can arise and thereby effect an explanation of the observational possibility that there might be two classes of bursts, not just one, (iii) how large the mean magnetic field is in a GRB, and (iv) whether particle acceleration in bursts is sufficiently rapid to account for the pervasive population of ultrarelativistic nuclei (cosmic rays) that shower Earth incessantly. This connection between the astrophysical environment of gamma-ray bursts and the underlying physics has not been studied before. In addition, this work will also address models for active galaxies, since their emission is probably driven by similar types of physics. Success in these goals will provide a suitable platform for further advancement of our knowledge of the exotic and alluring gamma-ray burst sources over the coming decades. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***

AST 0098705巴林伽马射线暴 (GRB) 是宇宙中已知的最迷人的天体之一，其短暂的本质具有独特性。大约 30 年前，他们的发现引发了一系列令人费解的谜团和令人震惊的真相。 其中最新的进展是 1997 年发现的 X 射线、光学和射电余辉的衰落，从而可以准确确定它们与地球的距离，将它们置于宇宙最遥远的领域。因此，天体物理学家得出的结论是，伽玛暴是宇宙中最明亮、最强大的天体。 目前的想法是，它们是由灾难性事件产生的，可能是大质量恒星的爆炸。 该项目的目标是研究伽玛暴的灾难性事件模型。 在这些模型中，当恒星喷射出的物质以高超音速和相对论速度冲入周围的环境气体时，伽玛暴就会发生，产生极其强大的宇宙冲击波。能量以热形式和极端相对论基本粒子的形式被释放。这些高速粒子随后产生辐射发射，在地球上以伽马射线、X射线、无线电波和可见光的形式被检测到。 这种耗散激波情景的不确定性主要源于两个限制：（i）瞬发伽马射线数据的持续时间相对较短且能量带宽较窄，以及（ii）目前理论模型的粗糙性。该项目解决了这些限制。它探讨了相对论粒子如何获得必要的极端能量。 它包括比以前更准确的可达到的最大能量的确定。它还试图在粒子加速特性和我们看到的辐射之间建立明确的相关性和趋势，使用后者作为加速物理学的诊断探针。这项工作试图回答的重大问题包括（i）GRB环境是否是一种有序的大规模现象，或者它是否拥有大量混沌、纠缠、磁化的细胞，（ii）这两种情况是否都可能出现，从而对可能存在两类爆发（而不仅仅是一种）的观测可能性进行解释，（iii）GRB中的平均磁场有多大，以及（iv）粒子是否存在 爆发的加速速度足够快，足以解释不断向地球喷洒的超相对论原子核（宇宙射线）的普遍存在。伽马射线暴的天体物理环境与基础物理之间的这种联系以前从未被研究过。此外，这项工作还将解决活跃星系的模型，因为它们的发射可能是由类似类型的物理驱动的。这些目标的成功将为我们在未来几十年内进一步增进对奇异且诱人的伽马射线爆发源的了解提供一个合适的平台。该项目的资金由 NSF 河外天文学和宇宙学计划 (AST/EXC) 提供。***