近日，美国乔治华盛顿大学Rachael E. Stewart团队报道了真空双折射和射电磁星偏振X射线发射。该研究于2026年8月5日发表在《自然》杂志上。

磁星是一类孤立中子星，其表面磁场极强，超过10¹⁴G（高斯）。其明亮的X射线辐射所探测的物理区域中，量子电动力学（QED）会影响辐射的传播。强磁场会诱导真空中与极化相关的折射率；这种真空双折射效应仍是QED一项长期存在但尚未被证实的预言。

研究组报道了通过协调成像X射线偏振探测者（IXPE）、中子星内部组成探测器（NICER）和帕克斯/穆里扬天文台的X射线和射电观测，对射电辐射磁星1E 1547.0−5408进行的相位和能量分辨的偏振测量。研究组在热主导的软X射线波段探测到很高的偏振度（PD），在2 keV处相位平均值达到65%，随后在2 keV至4 keV之间显著下降。在某些旋转相位，2–3 keV的偏振度升至近80%，而在射电波束穿越期间始终保持高水平（40%）。

相位依赖的X射线和射电极化角均与旋转矢量模型一致，表明发射几何结构追踪了恒星的大尺度磁场。总体而言，这些特征对使用光无折射传播至无穷远的标准表面发射模型提出了挑战。由真空双折射主导的磁层传播可以自然地解释X射线偏振信号。该结果标志着在探测QED这一标志性预言方面取得了显著进展，为超强场量子物理开辟了新的宇宙窗口，从而激励了该领域进一步的观测和理论研究。

附：英文原文

Title: Vacuum birefringence and the polarized X-ray emission from a radio magnetar

Author: Stewart, Rachael E., Dinh Thi, Hoa, Younes, George, Lower, Marcus E., Baring, Matthew G., Negro, Michela, Camilo, Fernando, Coley, Joel B., Enoto, Teruaki, Harding, Alice K., Ho, Wynn C. G., Hu, Chin-Ping, Kaaret, Philip, Scholz, Paul, Kooten, Alex Van, Wadiasingh, Zorawar

Issue&Volume: 2026-08-05

Abstract: Magnetars are isolated neutron stars with exceptionally strong surface fields exceeding 1014G (ref.1). Their bright X-ray emission probes physical regimes in which quantum electrodynamics (QED) influences radiation propagation2,3,4. Strong magnetic fields induce polarization-dependent refractive indices in the vacuum5,6; such vacuum birefringence remains a long-standing but unconfirmed prediction of QED. Here we report phase- and energy-resolved polarization measurements of the radio-emitting magnetar 1E 1547.05408 obtained by coordinating X-ray and radio observations from the Imaging X-ray Polarimetry Explorer, the Neutron Star Interior Composition Explorer and the Parkes/Murriyang Observatory. We detect large polarization degrees (PDs) in the thermally dominant soft X-ray band, reaching phase-averaged values of 65% at 2keV before substantially decreasing between 2keV and 4keV. At certain rotational phases, the 2–3keV PD rises to nearly 80% while remaining high (40%) throughout the radio beam crossing. The phase-dependent X-ray and radio polarization angles are both consistent with the rotating vector model, suggesting that the emission geometries track the large-scale magnetic field of the star. Collectively, these characteristics challenge standard surface emission models using non-refractive propagation of light to infinity. Vacuum-birefringence-governed magnetospheric propagation can naturally explain the X-ray polarization signals. Our results represent a marked advance in probing this hallmark prediction of QED, opening a new cosmic window into superstrong-field quantum physics, thereby motivating further observational and theoretical studies concentrating on this domain.

DOI: 10.1038/s41586-026-10859-z

Source: https://www.nature.com/articles/s41586-026-10859-z