发表机构
Xiamen University of Technology; Nanjing University（厦门理工学院; 南京大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文通过二维流体动力学模拟研究年轻重复FRB周围超新星遗迹环境的源局域DM演化，发现其DM随时间下降，且能匹配FRB 20190520B的观测特征。
AI 中文摘要
重复快速射电暴可能起源于年轻超新星遗迹（SNR）环境，其演化的等离子体对观测到的色散量（DM）有贡献。我们采用二维轴对称流体动力学模拟，研究年轻中子星的连续各向异性星风与同源膨胀的超新星抛射物之间的相互作用，追踪演化至约160年，并通过被动示踪剂分离星风与非星风贡献，计算不同观测方向上的源局域DM。在基准模型中，强极向聚焦的星风会膨胀出低密度腔，而被扫积的壳层大致呈圆形，DM呈现中等角度变化；DM主要由抛射物和被扫积的非星风物质主导。经立体角平均、扣除环境后的过量DM在整个演化过程中下降，最初数十年近似遵循t_age^-2，之后斜率略有变陡。星风与抛射物参数的变化会改变归一化值、早期演化和观测角依赖性，但所有模型中角度平均DM均呈下降趋势，不同双极星风轮廓产生的长期演化相似。对于FRB 20190520B，基准模型在约20年时达到与观测推断的源帧值相当的下降率，此时平均过量DM约为1.8×10² pc cm⁻³。因此，这类年轻环境可保留大量电子柱，同时产生快速长期下降；重复暴的多样性表明，超新星遗迹驱动的膨胀可能与其他时变等离子体结构或电离变化共存。
英文摘要
Repeating fast radio bursts may reside in young supernova remnant (SNR) environments whose evolving plasma contributes to the observed dispersion measure (DM). We use two-dimensional axisymmetric hydrodynamic simulations to study the interaction between a continuous anisotropic wind from a young neutron star and homologously expanding supernova ejecta. We follow the evolution to approximately 160 yr and calculate the source-local DM along different viewing directions, using a passive tracer to separate wind and nonwind contributions. In the fiducial model, the strongly polar-focused wind inflates a low-density cavity, while the swept-up shell remains broadly rounded and the DM shows moderate angular variation. The DM is dominated by ejecta and swept-up nonwind material. The solid-angle-averaged ambient-subtracted excess DM declines throughout the evolution, approximately following $t_{\rm age}^{-2}$ during the first several tens of years and becoming modestly steeper later. Variations in wind and ejecta parameters modify the normalization, early evolution, and viewing-angle dependence, but the angle-averaged DM declines in all models, while different bipolar wind profiles produce similar long-term evolution. For FRB 20190520B, the fiducial model reaches a decline rate comparable to the source-frame value inferred from observations at approximately 20 yr, when the mean excess DM is approximately $1.8\times10^2~{\rm pc,cm^{-3}}$. Thus, such a young environment can retain a substantial electron column while producing a rapid secular decrease. Repeater diversity suggests that SNR-driven expansion may coexist with additional time-dependent plasma structures or ionization changes.
Comments23 pages, 7 figures, 2 tables. Published in The Astrophysical Journal
Journal refThe Astrophysical Journal, 1009, 223 (2026)
