变脸活动星系核 1ES 1927+654 喷流形成期间射电极化的首次探测
First Detection of Radio Polarization During Jet Formation in the Changing-Look AGN 1ES 1927+654
- University of Maryland Baltimore County（马里兰大学巴尔的摩县分校）
- NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）
- Center for Space Science and Technology, University of Maryland Baltimore County（马里兰大学巴尔的摩县分校空间科学与技术中心）
- Center for Research and Exploration in Space Science and Technology, NASA/GSFC（NASA/戈达德太空飞行中心空间科学与探索研究中心）
- National Centre for Radio Astrophysics（国家射电天文中心）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
该研究通过VLBA和VLA多波段观测，首次在变脸活动星系核1ES 1927+654中探测到喷流形成期间的射电极化，证实其已转变为射电噪AGN并拥有新发射的相对论性喷流。
AI中文摘要：
我们展示了针对变脸活动星系核 1ES 1927+654 自2022年年中以来X射线重新增亮后的多波段射电研究，结合了VLBA成像与多波段和时间分辨的VLA观测。我们的主要结果如下：（i）VLBA观测继续揭示Meyer等人（2025）首次报道的双极喷流结构，新的X波段探测在更大分离距离上确认了该形态，K波段成像则揭示了一个与连续外流一致的发射桥；（ii）VLBA核心呈现GHz峰谱，VLA/VLITE在340 MHz至45 GHz的观测显示来自非均匀同步辐射源的发射，在约3 GHz以下自吸收，以上则为光学薄；（iii）在8 GHz以上，VLA和VLBA的通量密度一致，表明发射由致密核心主导；（iv）在约3 GHz以上探测到线偏振，偏振分数随频率从约0.2%增加到约6%，且电矢量位置角（EVPA）表现出非线性的λ²行为；（v）长期VLA X波段监测显示，2026年约81天内EVPA发生了约137度的大幅度平滑旋转，随后部分回转，总强度稳定且偏振分数被抑制在约1.4%以下，这与一个传播扰动穿过致密发射区相一致；（vi）在任何历元均未探测到圆偏振。这些观测表明，1ES 1927+654已从X射线主导的非喷流状态转变为射电噪活动星系核（Laha等人，2025），并拥有一个新发射的相对论性喷流，为研究喷流诞生和早期磁场演化提供了独特实验室。
英文摘要：
We present a multiwavelength radio study of the changing-look AGN 1ES 1927+654 following its renewed X-ray brightening since mid-2022, combining VLBA imaging with multi-band and time-resolved VLA observations. Our main results are: (i) VLBA observations continue to reveal the bipolar jet structure first reported in Meyer et al. (2025), with new X-band detections confirming the morphology at larger separation and K-band imaging revealing a bridge of emission consistent with a continuous outflow; (ii) the VLBA core exhibits a GHz-peaked spectrum, and VLA/VLITE observations from 340 MHz to 45 GHz show emission from an inhomogeneous synchrotron source, self-absorbed below ~3 GHz and optically thin above; (iii) VLA and VLBA flux densities are consistent above 8 GHz, indicating emission dominated by a compact core; (iv) linear polarization is detected above ~3 GHz, with fractional polarization increasing with frequency from ~0.2% to ~6% and EVPAs exhibiting non-linear lambda^2 behavior; (v) long-term VLA X-band monitoring reveals a large, smooth rotation of the EVPA of ~137 degrees over ~81 days in 2026, followed by a partial return, at stable total intensity and suppressed fractional polarization <~1.4%, consistent with a propagating disturbance crossing the compact emitting region; and (vi) circular polarization is not detected at any epoch. These observations demonstrate that 1ES 1927+654 has transitioned from an X-ray-dominated, non-jetted state to a radio-loud AGN (Laha et al. 2025) hosting a newly launched relativistic jet, a unique laboratory for studying jet birth and early magnetic field evolution.
