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实现了此前不可能的观测能力，首次通过法拉第旋转直接诊断了伽马暴喷流的内禀磁场相干尺度和周围致密磁化介质的性质，为理解伽马暴余辉磁场起源和前身星环境提供了全新的直接观测约束。
摘要明确报道了GRB 260310A射电余辉的首次厘米波偏振探测和首次法拉第旋转测量。在11-25 GHz探测到线偏振，偏振分数从(3.18 ± 0.18)%降至(0.69 ± 0.22)%。测得旋转测量值RM = -(8300 ± 90) rad m^-2，低偏振暗示喷流存在相干尺度θ_B ≍ 10^-2 rad的patchy磁场，RM大小与致密磁化环境（如前身星H II区）一致。
论文报道了伽马暴余辉中首个厘米波偏振和首个法拉第旋转测量，实现了此前不可能的观测能力并直接给出了喷流磁场相干尺度和环境磁化密度的物理诊断。结果实质性改变了领域对GRB磁场和环境的探测能力，摘要明确指出了未来数天至数周多频偏振监测的跟进价值，符合breaking标准。
ADS 2026ApJ..1006L...8C 后续多频偏振监测对磁场结构演化的约束
ADS 2026ApJ..1006L...8C 其他伽马暴余辉是否表现出类似的法拉第旋转和patchy磁场特征
伽马射线暴余辉中首次探测到法拉第旋转：GRB 260310A 的低偏振和高旋转量度揭示喷流磁场结构与环境
We report the detection of linear polarization in the radio afterglow of GRB 260310A, representing the first centimeter-wavelength polarization detection of a gamma-ray burst (GRB) afterglow and the first measurement of Faraday rotation in a GRB environment. We detect linearly polarized emission across 11─25 GHz, with a polarization fraction decreasing monotonically from (3.18 ± 0.18)% at 25 GHz to (0.69 ± 0.22)% at 11 GHz. We model the multiwavelength data as emission from a refreshed forward shock (FS) that dominates in the optical and X-rays and a reverse shock (RS) in a structured, relativistic jet that dominates at radio wavelengths. The observed depolarization toward the lower radio frequencies is consistent with suppression by RS synchrotron self-absorption, while the low observed polarization at high frequencies relative to the theoretical maximum suggests a patchy magnetic field in the jet with a coherence scale, θ<SUB>B</SUB> ≍ 10<SUP>−2</SUP> rad. We identify a frequency-dependent rotation of the polarization angle consistent with Faraday rotation, with a rotation measure (RM) of RM = −(8300 ± 90) rad m<SUP>−2</SUP> at the GRB redshift. The magnitude of the RM is consistent with propagation through a dense, magnetized environment, such as a progenitor H II region. These findings demonstrate that GRB afterglows exhibit measurable linear polarization at centimeter wavelengths, and that their polarimetric properties probe both intrinsic jet magnetization and the surrounding medium. Future multifrequency polarimetric monitoring over timescales of days to weeks will enable detailed studies of the evolution of magnetic field structure and provide new constraints on the role of magnetic fields in GRB afterglows.
展开 ▾首次在 GRB 余辉中探测到法拉第旋转，结合低偏振分数（约3%）和高旋转量度（约-8300 rad/m²），直接约束了喷流内磁场相干尺度和周围介质性质，为 GRB 偏振研究开辟了新窗口。
过去对 GRB 余辉的偏振研究主要集中在光学/近红外波段，已在少数事件中探测到反向激波主导的高偏振 Mundell+ 2013，而射电偏振探测长期停留在上限 van der Horst+ 2014，直到 ALMA 首次在毫米波测到反向激波偏振 Laskar+ 2019a，表明磁场相干尺度存在多样性。本文将 GRB 偏振研究推进到厘米波段，并首次探测到法拉第旋转，利用 Granot+ 2005 和 Burn 1966 的框架，推断喷流内的磁场相干角约 0.01 rad，且高旋转量度（RM ~ -8300 rad/m²）与 Harvey-Smith+ 2011 所报道的银河系 HII 区磁场特征一致，指向前身星周围致密、磁化环境。未来利用多频偏振监测（数天至数周），有望追踪喷流磁场结构的时间演化，为区分不同喷流模型及甄别前身星环境提供关键诊断。
预印本 2026-04-30 · 接收 2026-06-18 · 刊出 2026-07-14 · 收录 2026-07-22
Metastable cosmic strings are a common prediction of grand unified theories and act as a source of a gravitational-wave background (GWB) that can explain the 2023 pulsar timing array (PTA) signal. In this paper, we revisit the GWB signal from metastable strings, emphasizing the need to carefully distinguish between two different timescales: (i) <inline-formula><mml:math><mml:msub><mml:mi>t</mml:mi><mml:mrow><mml:mi>LB</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula>, the timescale of loop breaking because of spontaneous monopole nucleation on closed string loops, and (ii) <inline-formula><mml:math><mml:msub><mml:mi>t</mml:mi><mml:mrow><mml:mi>NC</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula>, the timescale of network collapse when string segments attached to monopoles begin to enter the Hubble horizon. We discuss under which conditions these two timescales are similar or far apart from each other and illustrate the resulting consequences for the GWB signal. In doing so, we generalize the description of the GWB signal from metastable strings to a three-parameter model in terms of the string tension <inline-formula><mml:math><mml:mi>G</mml:mi><mml:mi>μ</mml:mi></mml:math></inline-formula> and the timescales <inline-formula><mml:math><mml:msub><mml:mi>t</mml:mi><mml:mrow><mml:mi>LB</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula> and <inline-formula><mml:math><mml:msub><mml:mi>t</mml:mi><mml:mrow><mml:mi>NC</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula>, which allows us to unify the modeling of standard metastable strings with what is known as quasistable strings. In the limit of a large <inline-formula><mml:math><mml:msub><mml:mi>t</mml:mi><mml:mrow><mml:mi>LB</mml:mi></mml:mrow></mml:msub><mml:mo>/</mml:mo><mml:msub><mml:mi>t</mml:mi><mml:mrow><mml:mi>NC</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula> ratio, we, moreover, derive a compact analytical expression for the predicted GWB spectrum in excellent agreement with numerical results in the literature. We thus conclude that our new templates for the GWB spectrum from metastable strings can be readily used in the analysis of future PTA datasets.
展开 ▾亚稳宇宙弦的新引力波模板：环断裂与网络坍缩 · 本文区分了亚稳宇宙弦的两种时间尺度（环断裂和网络坍缩），提出三参数模型统一描述其引力波背景，并给出大时间尺度比下的解析谱公式，适用于未来PTA数据分析。
预印本 2026-04-30 · 刊出 2026-08-05 · 收录 2026-08-20
This article delves into the observational properties of a Schwarzschild-like black hole (BH). Initially, the research provides a succinct examination of the spacetime geometry and the configuration of its horizon. Furthermore, we study the photon dynamics around the Schwarzschild-like BH in the presence of plasma using the Hamiltonian formalism. We found that the photon sphere radii increase under the influence of plasma frequency and vice versa for the spacetime parameters. Further exploration is dedicated to understanding how plasma affects the shadow of the BH, and we find that the radius of the BH shadow shrinks with the rise of the ξ parameter and plasma frequency. We then turn to constraining the spacetime parameters and the plasma frequency by using the observational data released by the Event Horizon Telescope (EHT) collaboration for M87* and Sgr A*. Additionally, the research scrutinizes the phenomenon of gravitational weak lensing in the vicinity of a Schwarzschild-like BH, considering both uniform and non-uniform plasma scenarios. The outcomes demonstrate that the angle of deflection increases under the influence of a uniform plasma frequency, whereas the opposite is true for non-uniform plasma. In both scenarios, a rise in the spacetime parameters results in a decrease in the deflection angle. Finally, we investigate the magnification of the gravitationally lensed image. The effect of the spacetime parameters and plasma frequencies on the total magnification is the same as in the deflection angles. *This research is funded by the National Natural Science Foundation of China (NSFC) (U2541210)
展开 ▾等离子体对类史瓦西黑洞的阴影和引力弱透镜的影响 · 研究等离子体对类史瓦西黑洞阴影和引力弱透镜的影响，发现等离子体频率和时空参数对光子球、阴影半径、偏转角及放大率的作用，并用EHT数据约束参数。
刊出 2026-04-30 · 收录 2026-09-13
We numerically study a formation of near extremal horizons from a gravitational collapse of radially symmetric gravitational waves in <inline-formula> <mml:math><mml:mrow><mml:mn>4</mml:mn><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math></inline-formula> dimensions within the framework of pure Einstein gravity with positive cosmological constant. Evolution of a regular initial data with cosmological horizon leads to a formation of a black hole with mass exceeding <inline-formula> <mml:math><mml:mrow><mml:mn>99</mml:mn><mml:mi>%</mml:mi></mml:mrow></mml:math></inline-formula> of the extremal value corresponding to the black hole and cosmological horizons coinciding. We demonstrate how our results fit within the framework of characteristic gluing, and present some evidence that the third law of black hole thermodynamics may not hold in the cosmological context, where the extremality corresponds to the maximal mass of the Schwarzschild black hole in de-Sitter space.
展开 ▾4+1维近极端引力坍缩：Schwarzschild-de-Sitter空间 · 数值研究4+1维纯爱因斯坦引力正宇宙学常数下径向对称引力波坍缩形成质量超过极端值99%的近极端黑洞，并给出特征拼接及宇宙学背景下热力学第三定律可能不成立的证据。
预印本 2026-04-30 · 接收 2026-08-03 · 刊出 2026-08-17 · 收录 2026-08-22