标题： X射线光谱定时变化在2020年巨大爆发期间的1A 0535+262 显示英文标题

标题： X-ray spectral-timing variability of 1A 0535+262 during the 2020 giant outburst

摘要： 在2020年11月，Be/X射线双星1A 0535+262经历了巨大的X射线爆发，峰值达到$\sim1\times 10^{38}$ erg s$^{-1}$ (1--100 keV, 1.8 kpc)，这是该源迄今为止记录到的最明亮的爆发。我们的目标是寻找相关的光谱和时间行为模式，这些模式可用于表征硬X射线瞬变脉冲星的吸积状态。我们研究了使用硬度-强度图和源的非周期性变化的光谱连续发射演化。硬度-强度图显示了三个不同的分支，可以与不同的吸积制度相区分。噪声成分的特征频率与光度相关。我们的观测涵盖了这一相关性的最高端，在之前未被采样的光度下进行。我们发现在此高光度下相关性有平坦化的证据，这可能表明在爆发峰值期间，吸积盘达到了离中子星表面最近的距离。我们还发现了光谱和时间参数中的滞回现象：在相同的光度水平下，爆发上升阶段的光谱更硬，特征噪声频率更大。 显示英文摘要

摘要： The Be/X-ray binary 1A 0535+262 underwent a giant X-ray outburst in November 2020, peaking at $\sim1\times 10^{38}$ erg s$^{-1}$ (1--100 keV, 1.8 kpc), the brightest outburst recorded for this source so far. Our goal is to search for patterns of correlated spectral and timing behavior that can be used to characterize the accretion states in hard X-ray transient pulsars. We have studied the evolution of the spectral continuum emission using hardness-intensity diagrams and the aperiodic variability of the source. The hardness-intensity diagram displays three distinct branches that can be identified with different accretion regimes. The characteristic frequency of the noise components correlates with the luminosity. Our observations cover the highest end of this correlation, at luminosities not previously sampled. We have found evidence for a flattening of the correlation at those high luminosities, which might indicate that the accretion disk reached the closest distance from the neutron star surface during the peak of the outburst. We also find evidence for hysteresis in the spectral and timing parameters: at the same luminosity level, the spectrum is harder and the characteristic noise frequency larger during the rise than during the decay of the outburst.