超新星遗迹相对论性粒子的高能辐射机制

High-energy radiation is directly connected with cosmic rays and is the powerful probe for studying the origin of cosmic rays. In the last decade, thanks to the development of the space-borne and ground-based high-energy telescopes, more and more gamma-ray-bright supernova remnants (SNR) were found in the GeV–TeV band, making research on gamma-ray emission from SNRs one of frontiers in modern astrophysics. In this project, we want to study the radiation mechanism of the high-energy emission from SNRs and explore the hadronic gamma-ray component to study the acceleration site and process of the cosmic-ray particles. Firstly, we study the spectral and spacial features of the gamma-ray emission from the young SNRs, such as RCW 86, RX J0852.0-4622, explore the hadronic gamma-ray component and constrain the energy conversion efficiency in young supernova remnants. Secondly, we study the diffusion process of cosmic rays in the molecular clouds (MCs) and predict the spectral and spacial distribution of the gamma-ray emission from the clouds illuminated by the cosmic-ray protons. Appling to the SNR-MC system, we may make a choice between the crushed cloud model and the escape-diffusion model and give a constraint on the spectral index of the protons accelerated by the SNR shock. Thirdly, we study the non-thermal bremsstrahlung emission from the keV-MeV electrons, drive the properties and the distribution of the parent electrons via fitting the observational data.

高能辐射直接和宇宙线粒子相关，是研究宇宙线起源的重要探针。得益于地基和空间高能望远镜的发展，近十年来越来越多的超新星遗迹在伽马射线波段被发现，使得超新星遗迹伽马射线研究成为热门领域之一。本项目旨在研究超新星遗迹的高能辐射机制，甄别来自高能质子的强子辐射成分，找寻超新星遗迹加速质子的证据，探究粒子加速过程。首先，我们研究诸如RCW 86、RX J0852.0-4622等这类年轻遗迹的伽马射线能谱和空间分布特征，找寻强子成分并以此给出这类年轻遗迹的能量转化效率。其次，我们研究宇宙线在分子云中的传播扩散过程，给出能谱和空间分布，并应用到与超新星遗迹相作用的分子云中，通过和观测比较区分直接打击和扩散打击这两类强子模型，对加速粒子的谱指数给出限制。最后，我们研究keV-MeV电子的非热轫制辐射性质，通过拟合观测数据来确定父粒子能谱及性质。

超新星遗迹一直被认为是河内宇宙线的主要贡献源，即能作为PeV加速器，但至今仍缺乏关键性的观测证据。而超新星遗迹的伽马射线研究是检验宇宙线的超新星遗迹起源学说的重要手段之一。本项目主要研究超新星遗迹的伽马射线辐射特征，具体有以下工作内容和结果：1）研究了SN 1006、RCW 86、RX J0852.0-462等年轻超新星遗迹的伽马射线辐射特征，得到了遗迹中的电子能谱的演化规律；2）构建了考虑逆激波加速粒子的双发射区模型，解释了典型的年轻超新星遗迹Cas A的多波段能谱，在双发射区模型下，Cas A仍然可作为PeV加速器的候选体；3）研究解释了包含ASgamma实验探测的百TeV以上辐射的Crab的多波段能谱，并根据百TeV以上的伽马射线数据限制了实心型超新星遗迹Crab中的强子加速效率；4）研究解释了ASgamma实验探测的来自超新星遗迹G106.3+2.7的超高能辐射，该遗迹成为超新星遗迹中的第一个PeV加速器候选体。