Radiative shocks in gamma-ray bursts

伽马射线暴（GRB）是宇宙爆炸的一种极端形式，可能是迄今为止发现的最强大的事件。 经过大量的工作，伽马射线暴现在已经知道在很远的地方，宇宙大小的重要部分。它们来自于由短寿命的致密源射出的非常高速的物质射流，可能是在黑洞形成期间。 至少在某些情况下，伽玛暴与沃尔夫-拉叶型的超大质量恒星的坍缩有关。 这项工作应该在GRB理论的一个主要目标上取得变革性进展，即利用从低能量（长波长，无线电数据）到最高能量（短波长，伽马射线）的所有可用观测数据，重建爆炸，确定射流的组成，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初期将学习复杂的理论和计算机模拟，有助于理解基础物理和极端条件下物质的性质。本研究将重新审视伽玛暴的冲击机制，并分析其辐射特性。 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，这些模拟将充分描述耗散机制和产生的辐射。 然后将对照观察结果对这些结果进行检验。 这项研究包括对所观察到的GRB中GeV闪光的机制进行研究，这已经提出了关于GRB爆炸外部冲击波物理学的新问题，特别是提出了具有强烈前兆并涉及超高能电子-正电子对的非线性冲击的可能性。 模拟方法和冲击机制都是新颖的，可能会发现爆炸波机制中意想不到的功能。 这项研究通过理解极端条件下物质的新性质来影响基础物理学。 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.