AI 中文总结
研究伽马射线暴和潮汐瓦解事件中脉冲相对论喷流在分层介质中传播时激波对余辉极化的影响，通过分析光变曲线和极化曲线，发现极化水平变化及时间特征，可辅助限制视角和介质分层，促进联合建模。
AI 中文摘要
伽马射线暴（GRBs）和至少一些潮汐瓦解事件（TDEs）是涉及脉冲相对论喷流的高能瞬变现象。喷流在周围介质中传播时会驱动相对论性前向激波，产生多波长极化同步辐射，即余辉。分析余辉光变曲线及其极化曲线可揭示GRB或TDE系统的几何性质。多数余辉极化测量针对长GRBs，其大质量恒星前身星风会形成分层外部介质，此类环境下的极化研究较少。本文探讨激波在分层介质中传播对脉冲相对论喷流余辉极化的影响。发现对于平顶和结构化喷流，多数情况下极化水平降低，时间特征与均匀外部介质相比在更长时间尺度上演变。极化在光变曲线几何转折附近达到峰值，观测极化演变时间尺度有助于限制视角和外部介质分层。这种考虑更现实系统的复合模型能更好地补充余辉光变曲线并促进这些可观测量的联合建模。
英文摘要
Gamma-ray bursts (GRBs) and at least some tidal disruption events (TDEs) are highly energetic transients involving impulsive relativistic jets. As these jets propagate into their surrounding media, they drive a relativistic forward shock into it, which radiates multi-wavelength polarized synchrotron emission, known as an afterglow. Analyzing the afterglow light curve along with its polarization curve can shed light on the geometrical properties of the GRB or TDE system such as the magnetic field structure behind the shock, the jet angular structure and even distinguish between proposed scenarios of delayed radio emission seen in some TDEs. While most afterglow polarization measurements are for long GRBs, whose massive star progenitor winds are expected to form a stratified external medium, the polarization from such environments is largely unexplored. Similarly, stratified media surround jetted TDEs. In this work we explore how shock propagation into a stratified medium affects the observed afterglow polarization from impulsive relativistic jets. We find that for both top hat and structured jets, in most cases the polarization levels are reduced and its temporal signature evolves on longer time scales compared to a uniform external medium. The polarization peaks at times close to a geometrical break in the light curve, indicating measurements during this time probe the maximal levels of polarization possible for the system. In addition, observationally capturing the polarization evolution time scales can assist in constraining our viewing angle and the external medium stratification. Such composite models, that account for more realistic systems that are motivated by light curve fittings, will allow us to complement afterglow light curves better and promote joint modeling of these observables.
Comments13 pages, 12 figures
