We report on new Very Long Baseline Interferometry radio measurements of supernova 2014C in the spiral galaxy NGC 7331, made with the European VLBI Network ~5 yr after the explosion, as well as on flux density measurements made with the Jansky Very Large Array (VLA). SN 2014C was an unusual supernova, initially of Type Ib, but over the course of ~1 yr it developed strong H$α$ lines, implying the onset of strong interaction with some H-rich circumstellar medium (CSM). The expanding shock-front interacted with a dense shell of circumstellar material during the first year, but has now emerged from the dense shell and is expanding into the lower density CSM beyond. Our new VLBI observations show a relatively clear shell structure and continued expansion with some deceleration, with a suggestion that the deceleration is increasing at the latest times. Our multi-frequency VLA observations show a relatively flat powerlaw spectrum with $S_ν\propto ν^{-0.56 \pm 0.03}$, and show no decline in the radio luminosity since $t\sim1$ yr.
We present broadband radio flux-density measurements supernova (SN) 1996cr, made with MeerKAT, ATCA and ALMA, and images made from very long baseline interferometry (VLBI) observations with the Australian Long Baseline Array. The spectral energy distribution of SN 1996cr in 2020, at age, $t \sim$8700 d, is a power-law, with flux density, $S \propto ν^{-0.588 \pm 0.011}$ between 1 and 34 GHz, but may steepen at $>35$ GHz. The spectrum has flattened since $t = 5370$ d (2010). Also since $t = 5370$ d, the flux density has declined rapidly, with $S_{\rm 9 \, GHz} \propto t^{-2.9}$. The VLBI image …
Shocks in the Symbiotic Recurrent Nova V3890 Sgr: VLBI Radio Imaging and Fermi GeV Gamma-Rays
Michigan State University（密歇根州立大学）；Institute for Advanced Study, Princeton（普林斯顿高等研究院）；Columbia University（哥伦比亚大学）；National Radio Astronomy Observatory（美国国家射电天文台）；Flatiron Institute（平顿研究所）；Chalmers University of Technology（查尔姆斯理工大学）
Fossil shell in 3C 84 as TeV $γ$-ray emitter and cosmic-ray accelerator
我们探索了受冲击的外部介质的物理特性（即，3C 84中与1960年左右出生的周期性射电瓣有关的一个壳）。在Ito等人先前的工作中，我们研究了在中央发动机停止喷气发射后这种壳层的动力学和辐射演化，我们发现化石壳层的辐射与快速衰落的射电瓣的辐射相似。我们将这个模型应用于3C 84，发现：（1）由数密度为0.3 cm $^{-3}$的冲击扩散环境物质构成的化石壳层，以来自中心致密区的射电辐射种子光子为辐射源，辐射出明亮的逆康普顿（IC）辐射，IC辐射超过切伦科夫望远镜阵列（CTA）的灵敏度阈值。(ii)当化石壳产生于数密度为$10^{3}$ cm $^{-3}$的几何厚电离等离子体中时，壳中的场强在磁场放大的存在下可达到约17 mG，射电发射变得与深成像VLBI观测的灵敏度相当。超高能宇宙射线（UHECRs）的可能产生的致密冲击等离子体也被认为是。
