AI 中文总结
本研究利用 CHIME 观测数据，扩展 FRB 样本后分析其光谱偏振特性，发现多数重复 FRB 处于复杂磁电离环境，非重复 FRB 退极化特征与重复源存在差异，指出需超宽带偏振测量深化认知。
AI 中文摘要
快速射电暴（FRB）是神秘的毫秒级射电瞬变，其偏振特性为探究其起源与环境提供关键线索。特别是由参数σ_RM量化的低频退极化，可探测 FRB 前身星周围复杂的磁电离介质，且已在一批重复 FRB 中观测到。我们利用加拿大氢强度测绘实验（CHIME）的观测数据，对重复和非重复 FRB 开展系统光谱偏振分析。针对 28 个重复 FRB，我们测量了 σ_RM，将已知样本从 14 个扩展至 36 个源（增幅达 2.6 倍）。重复源总体的核密度估计（KDE）峰值为 1.3 rad m⁻²，约 70% 的源呈现 σ_RM ≳ 1 rad m⁻²，表明多数重复 FRB 处于复杂磁电离环境中。针对 70 个非重复 FRB，我们研究了 4 种光谱偏振模型，未发现任何源呈现 σ_RM ≳ 5 rad m⁻² 的显著退极化现象，约一半非重复 FRB 的线性偏振度在全频带内保持一致。不过我们提醒，这些结果可能受 CHIME 有限的频率覆盖范围影响。未来覆盖宽间隔频率的超宽带偏振测量，将克服当前观测偏差，实现 σ_RM 的精确测量，大幅深化我们对 FRB 环境的理解。
英文摘要
Fast radio bursts (FRBs) are enigmatic millisecond-duration radio transients whose polarization properties offer crucial insights into their origins and environments. In particular, low-frequency depolarization---quantified by the parameter \(σ_{\mathrm{RM}}\)---probes the complex magneto-ionic medium surrounding the progenitor, and has been observed across a population of repeating FRBs. We present a systematic spectro-polarimetric analysis of repeating and non-repeating FRBs using observations from the Canadian Hydrogen Intensity Mapping Experiment (CHIME). For 28 repeating FRBs, we measure \(σ_{\mathrm{RM}}\), expanding the known sample from 14 to 36 sources (an increase by a factor of 2.6). The kernel density estimate (KDE) of the repeating population peaks at \(1.3\ \mathrm{rad\,m^{-2}}\), with approximately 70\% of the sources showing \(σ_{\mathrm{RM}} \gtrsim 1\ \mathrm{rad\,m^{-2}}\), implying that most reside in complex magneto-ionic environments. For 70 non-repeating FRBs, we investigate four spectro-polarimetric models; no source exhibits significant depolarization with \(σ_{\mathrm{RM}} \gtrsim 5\ \mathrm{rad\,m^{-2}}\). Roughly half of the non-repeaters are consistent with a constant linear polarization fraction across frequency. We caution, however, that these results may be affected by the limited frequency coverage of CHIME. Future ultra-wideband polarimetry, spanning widely separated frequencies, will overcome current observational biases, enable precise \(σ_{\mathrm{RM}}\) measurements, and substantially deepen our understanding of FRB environments.
