Supernova Shock Wave and Radiative Interactions

超新星（SNe）是结束大质量恒星生命的爆炸。研究它们很重要，因为超新星在星系中散布了恒星和爆炸中产生的原子元素，它们有助于天文学家了解恒星是如何进化和死亡的。天文学家研究超新星的方法之一是观察SNe中喷出的物质如何与恒星周围的气体物质相互作用，从而产生冲击波。为了帮助解释这些观测结果，弗吉尼亚大学的一个研究小组将开展一个项目，研究超新星与致密的星周介质之间的相互作用。他们的研究将包括流体力学的计算机模拟，电磁辐射形式的能量传递建模，以及冲击物理条件的计算。通过更好地定义这些事件中涉及的星周介质的性质，这项研究试图填补恒星演化理论的空白。首席研究员将在大学附近的麦考密克天文台（McCormick Observatory）做年度公开讲座，并在无障碍地点为老年人做讲座。一名研究生和一名本科生将参与研究，并将学习理论天体物理学中使用的技术，以及解决开放性问题的方法。该项目的目标是研究超新星与密集的、可能具有光学厚度的星周介质之间的相互作用。物理条件比通常在超新星相互作用中遇到的更为极端，质量损失区的结构可能是复杂的。研究人员将为相互作用的条件和结构开发诊断方法。将讨论的具体主题包括当冷却很重要时冲击波结构和流体动力不稳定性，x射线和紫外线/光学冲击发射的一致模型，冲击前电离和发射，非热粒子和无线电发射和吸收，以及尘埃辐射加热的红外发射。这些模型将与从无线电到x射线的多波长观测结果进行比较。这项研究将把观测到的相互作用超新星的发现与驱动超新星前质量损失的合理机制联系起来。具有窄线特征的超新星被推断为具有致密的、缓慢移动的星周介质。这些特征可以在很多类型的超新星上观察到，包括那些有氢谱线和没有氢谱线的超新星、超亮超新星、具有Ia型特征的超新星，以及可能的低能超新星。对于这些事件，尽管窄线超新星占II型超新星的9%，但无论是驱动质量损失的机制还是超新星发生的时间都不清楚。通过更好地定义这些事件中涉及的星周介质的性质，这项研究试图填补恒星演化理论的空白。此外，致密介质中物理过程的各个方面应该更广泛地适用，例如适用于活动星系核中的致密介质。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Supernovae (SNe) are explosions that end the lives of massive stars. They are important to study since supernovae seed the galaxy with atomic elements made in the star and in the explosion, and they help astronomers to understand how stars evolve and die. One of the ways astronomers study supernovae is by observing how the matter ejected in the SNe interacts with the gaseous material surrounding the star, producing a shock wave. In order to help to interpret such observations, a research team at the University of Virginia will carry out a program to investigate the interaction of a supernova with a dense circumstellar medium. Their study will include hydrodynamic computer simulations, modeling of energy transfer in the form of electromagnetic radiation, and calculations of physical conditions in the shock. By better defining the nature of the circumstellar media involved in these events, this research seeks to fill gaps in stellar evolution theory. The principal investigator will give annual public lectures at the McCormick Observatory, near the university, as well as talks for elderly persons given at accessible sites. A graduate student and an undergraduate student will be involved in the research and will learn techniques used in theoretical astrophysics, as well as ways of approaching open questions. The goal of the project is to investigate the interaction of a supernova with a dense, possibly optically thick, circumstellar medium. The physical conditions are more extreme than ordinarily encountered in supernova interactions and the structure of the mass loss region is probably complex. The researchers will develop diagnostics for the conditions in and structure of the interaction. Specific topics that will be addressed include the shock wave structure and hydrodynamic instabilities when cooling is important, consistent models for X-ray and ultraviolet/optical shock emission, pre-shock ionization and emission, nonthermal particles and radio emission and absorption, and infrared emission from the radiative heating of dust. The models will be compared to multiwavelength observations, from radio to X-rays. The research will relate the findings for observed interacting supernovae to plausible mechanisms for driving the pre-supernova mass loss. Supernovae that have narrow line characteristics are inferred to have a dense, slow moving circumstellar medium. These characteristics are observed over a broad range of supernova types, including those with and without hydrogen lines, superluminous supernovae, supernovae with Type Ia characteristics, and possible low energy supernovae. For these events, neither the mechanism driving the mass loss nor the timing with the supernova is understood, although narrow line supernovae make up about 9% of Type II supernovae. By better defining the nature of the circumstellar media involved in these events, this research seeks to fill gaps in stellar evolution theory. In addition, aspects of the physical processes in dense media should be more broadly applicable, for example to the dense media in active galactic nuclei.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.