4U 1538-52的心跳：来自XMM-Newton和NuSTAR的宽带X射线光谱特性
4U 1538-52 in a Heartbeat: Broadband X-ray Spectral Properties from XMM-Newton and NuSTAR
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中文总结 AI 辅助
本研究结合XMM-Newton和NuSTAR观测，对HMXB 4U 1538-52下合相位开展宽带X射线光谱分析，揭示其吸积物质的团块与结构，相关结果获3D流体模拟支持。
中文摘要 AI 辅助
银河系高-mass X射线双星（HMXB）是研究致密天体吸积机制以及大质量恒星复杂星风的重要系统。特别是，拥有中子星的HMXB能让我们揭示X射线脉冲星中吸积物质的结构，进而研究物质在极端压力和密度条件下的行为，这是XRISM和NewAthena的主要科学目标。本文报道了对HMXB 4U 1538-52的首次食外XMM-Newton观测，并结合了NuSTAR的覆盖数据。我们的观测 campaign旨在在中子星下合这一关键轨道相位，通过高分辨率光谱研究星风的变异性和连续谱的变化。得益于同时覆盖软X射线和硬X射线的观测，我们获得了迄今为止4U 1538-52中吸积物质最详细的X射线视图。特别是，我们进行了降至中子星脉冲周期的时间分辨光谱分析，以凸显星风团块特性和吸积结构。在该数据集中，我们观测到一个亮度约为10^37 erg·s^-1的明亮耀斑，可能由10^20 g的团块吸积引发，随后形成一个心跳状事件的光度下降。该事件之后出现三个局部吸收峰，其局部变异性与脉冲周期相当，且整个观测过程中基础光谱逐渐变硬。这可能表明中子星附近存在小尺度和大尺度的高密度结构，可归因于嵌入吸积尾流中的团块和丝状结构。这些观测证据得到了3D流体动力学模拟的进一步支持和重现。
英文摘要
Galactic high-mass X-ray binaries (HMXBs) are important systems for studying accretion mechanisms onto compact objects and for investigating the complex stellar winds of massive stars. In particular, HMXBs hosting a neutron star allow us to reveal the structure of the accreted material in X-ray pulsars and consequently to investigate how matter behaves under extreme conditions of pressure and density. These are major scientific goals for XRISM and NewAthena. Here we report on the first out-of-eclipse XMM-Newton observation of the HMXB 4U 1538-52, complemented by NuSTAR coverage. Our campaign aimed to investigate stellar-wind variability and continuum changes with high-resolution spectroscopy at a critical orbital phase: when the neutron star is in inferior conjunction. Thanks to simultaneous observations covering both soft and hard X-rays, we obtain the most detailed X-ray view of the accreted material in 4U 1538-52 to date. In particular, we perform time-resolved spectroscopy down to the pulse period of the neutron star to highlight wind clumping properties and accretion structures. In this dataset, we observe a bright flare reaching $\sim$10$^{37}\,\rm{erg\,s^{-1}}$ probably induced by the accretion of a $10^{20}\,\rm{g}$ clump, followed by a luminosity dip forming a heartbeat-like episode. This event is followed by three local absorption peaks with local variability of the order of the pulse period, and a gradual hardening of the underlying spectrum throughout the observation. This could indicate the presence of both small-scale and large-scale overdense structures in the vicinity of the neutron star, which can be attributed to clumps and filamentary structures embedded in the accretion wake. These observational evidences are further supported and reproduced by 3D hydrodynamic simulations.
