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arXiv 2201.04169astro-ph.HE
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大质量X射线双星船帆座X-1中的连续谱、回旋线和吸收变化

Continuum, cyclotron line, and absorption variability in the high-mass X-ray binary Vela X-1

C. M. Diez, V. Grinberg, F. Fürst, E. Sokolova-Lapa, A. Santangelo, J. Wilms, K. Pottschmidt, S. Martínez-Núñez, C. Malacaria, P. Kretschmar

摘要:

Vela X-1具有复杂的星云风、显著的回旋共振散射特性、内禀变率和方便的物理参数(近距离、大倾角、小轨道间距),便于对该系统进行观测和分析,是研究各种尺度下高质量X射线双星吸积过程的关键系统之一。我们重新审视船帆座X-1与NuSTAR在轨道相位~0.68-0.78和~0.36-0.52的两个新的观测,这表明了过多的变化,使我们能够研究吸积几何和恒星风系统的属性。我们遵循的光谱参数的演变到脉冲周期的时间尺度使用部分覆盖的幂律连续与费米-狄拉克截止模型的连续和局部吸收。我们可以确认光子指数和光度之间的反相关性,低通量,折叠能量和光度之间,这意味着在康普顿等离子体的性质的变化。我们无法确认先前观察到的回旋加速器线能量与整个观测中的源亮度之间的相关性,但我们观察到在强烈耀斑之后回旋加速器线能量下降。我们看到两次观测之间以及一次观测(约0.36-0.52轨道相位)内吸收的强烈变化,这可以通过大尺度结构的存在来解释,例如系统中的吸积和光电离尾流以及我们通过该结构的可变视线。

英文摘要:

Because of its complex clumpy wind, prominent cyclotron resonant scattering features, intrinsic variability and convenient physical parameters (close distance, high inclination, small orbital separation) which facilitate the observation and analysis of the system, Vela X-1 is one of the key systems to understand accretion processes in high-mass X-ray binaries on all scales. We revisit Vela X-1 with two new observations taken with NuSTAR at orbital phases ~0.68-0.78 and ~0.36-0.52 which show a plethora of variability and allow us to study the accretion geometry and stellar wind properties of the system. We follow the evolution of spectral parameters down to the pulse period time-scale using a partially covered powerlaw continuum with a Fermi-Dirac cut-off to model the continuum and local absorption. We could confirm anti-correlations between the photon index and the luminosity and, for low fluxes, between the folding energy and the luminosity, implying a change of properties in the Comptonising plasma. We could not confirm a previously seen correlation between the cyclotron line energy and the luminosity of the source in the overall observation, but we observed a drop in the cyclotron line energy following a strong flare. We see strong variability in absorption between the two observations and within one observation (for the ~0.36-0.52 orbital phases) that can be explained by the presence of a large-scale structure, such as accretion- and photoionisation wakes in the system and our variable line of sight through this structure.

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