Radiative shocks in gamma-ray bursts

伽马射线暴(GRB)是宇宙爆炸的一种极端形式，也可能是迄今发现的最强大的事件。经过大量的研究，现在已知伽玛暴距离很远，相当于宇宙大小的一小部分。它们来自极高速的物质喷流，这些物质可能是在黑洞形成期间由短暂的致密源喷出的。至少在某些情况下，伽玛暴与被称为沃尔夫-瑞叶的超大质量恒星的崩塌有关。这项工作应该在伽玛暴理论的一个主要目标上取得革命性的进展，即利用从低能量(长波、射电数据)到最高能量(短波、伽马射线)的所有可用观测来重建爆炸，确定喷流的组成，它们是如何形成的，它们如何发射伽马射线，以及它们如何与周围环境相互作用。初级研究人员在职业生涯的初期将学习复杂的理论和计算机模拟，并有助于理解基本物理和极端条件下物质的性质。这项研究将重新探讨伽玛暴中的激波机制，并分析它们的辐射特性。它将使用从头算数值模拟来研究一种新型的亚光球激波。通过在微观水平上跟踪激波的形成和传播，这些模拟将全面描述耗散机制和产生的辐射。然后将根据观察结果对这些结果进行测试。这项研究包括关于在伽玛暴中观测到的GeV闪光的机制的工作，这已经对伽玛暴爆炸的外部冲击波的物理提出了新的问题，特别是提出了具有强烈前驱并涉及超高能电子-正电子对的非线性冲击的可能性。模拟方法和冲击机理都是新颖的，有可能揭示爆炸波机理中意想不到的特征。这项研究通过了解极端条件下物质的新属性来影响基础物理学。教育影响包括培训初级研究人员和将成果纳入教学课程。

Gamma-ray bursts (GRBs) are an extreme variety of cosmic explosion and perhaps the most powerful events yet discovered. After a lot of work, GRBs are now known to be at large distances, significant fractions of the size of the universe. They come from very high speed jets of material shot out by short-lived compact sources, possibly during the formation of black holes. At least in some cases, GRBs are associated with the collapse of very massive stars of the type called Wolf-Rayet. This work should make transformative progress on a major goal of GRB theory, which is to use available observations all the way from low energies (long wavelengths, radio data) to the highest energies (short wavelength, gamma rays), to reconstruct the explosion, determining the composition of the jets, how they are made, how they emit gamma rays, and how they interact with their surroundings. Junior researchers at the beginning of their careers will learn about complex theories and computer simulations and contribute to the understanding of fundamental physics and the properties of matter in extreme conditions.This research will revisit the mechanism of shocks in GRBs, and analyze their radiative properties. It will use ab initio numerical simulations to investigate a new type of sub-photospheric shock. By following shock formation and propagation on a microscopic level, these simulations will fully describe the dissipation mechanism and the radiation produced. These results will then be tested against observations. The study includes work on a mechanism for the observed GeV flashes in GRBs which has already raised new questions about the physics of the external blast waves from GRB explosions, and in particular suggests the possibility of a non-linear shock which has a strong precursor and involves ultra-high-energy electron-positron pairs. Both the simulation method and the shock mechanism are novel and could potentially uncover unexpected features in the blast wave mechanism. The research impacts fundamental physics by understanding new properties of matter in extreme conditions. Educational impacts include the training of junior researchers and incorporation of results into instructional courses.