发表机构
Anton Pannekoek Institute for Astronomy; Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics; School of Physics and Technology, Wuhan University（安东·潘内科克天文学研究所; 卡尔·雷米斯天文台与埃尔朗根高能粒子物理中心; 武汉大学物理科学与技术学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用NICER和Insight-HXMT同时观测MAXI J1820+070，发现其低傅里叶频率下软（<1 keV）与硬（>100 keV）X射线通量呈反相关，为理解黑洞X射线双星日冕动力学提供新约束。
AI 中文摘要
黑洞X射线双星（BHXRBs）在硬态下表现出跨宽能量范围的X射线发射变化。硬X射线被认为是由热X射线日冕对来自吸积盘的种子光子进行康普顿逆散射产生的，从而形成大致呈幂律形状且带有高能截断的光谱成分。对日冕变异性进行完整研究需要看到光谱的全貌，从种子光子能量处的低能截断到可能与日冕温度相关的高能截断。我们针对明亮的BHXRB MAXI J1820+070，利用NICER和Insight-HXMT严格同时的观测，进行了详细的谱定时研究，覆盖0.3-250 keV能量范围。高数据质量使我们能够研究整个X射线波段的时延和相干性。我们发现，在低傅里叶频率（$\lesssim0.02$ Hz）下，低于1 keV的软X射线通量与高于100 keV的硬X射线通量呈反相关，即相位时延为$|π|$弧度。当比较1 keV以上的能带时，未观察到反相关。我们考虑了若干解释该观测到的复杂行为的机制，例如日冕截断能量受吸积盘调制、幂律枢转以及非热电子的贡献。未来基于观测效应进行更详细的建模工作，可能为吸积黑洞周围X射线发射区域的动力学提供新的约束。
英文摘要
Black hole X-ray binaries (BHXRBs) in the hard state show variable X-ray emission across a wide range of energies. Hard X-rays are thought to be produced through Compton-upscattering of seed photons from the accretion disc by the hot X-ray corona, leading to a spectral component roughly shaped like a power-law with a high-energy cut-off. A complete study of the coronal variability requires a full view of the spectrum, from the low-energy cut-off at the seed photon energy to the high energy cut-off, which may be related to the coronal temperature. We present a detailed spectral-timing study of strictly simultaneous observations by NICER and Insight-HXMT of the bright BHXRB MAXI~J1820+070, covering the 0.3-250 keV energy range. The high data quality allows us to study the lags and coherence across the full X-ray band. We find that at low Fourier frequencies ($\lesssim0.02$ Hz), the soft X-ray flux below 1 keV and hard X-ray flux above 100 keV are anticorrelated, i.e. phase lags of $|π|$ rad. No anticorrelation is observed when comparing energy bands above 1 keV. We consider several explanations for the observed complex behaviour, such as a modulation of the coronal cut-off energy by the disc, power-law pivoting and a contribution from non-thermal electrons. Future, more detailed modelling efforts based on the observed effects may place new constraints on the dynamics of the X-ray emitting regions around accreting black holes.
Comments14 pages, 6 figures, accepted for publication in MNRAS
