[论文解读] Fundamental properties of High-Mass X-ray Binaries

A. Gónzalez-Galán|arXiv (Cornell University)|Feb 26, 2015

Astrophysical Phenomena and Observations被引用 9

一句话总结

本博士论文研究了四个大质量X射线双星系统——其中三个为超巨星快变X射线暂现源（SFXTs），一个为中等性质源——以探究其X射线变异性背后的物理成因。通过分析轨道解、Halpha风变异性、恒星大气结构以及X射线通量的轨道调制，本研究发现风过程与恒星成分差异才是驱动X射线行为的关键因素，而非轨道偏心率，支持系统属性为连续分布而非离散子类的观点。

ABSTRACT

The aim of this PhD Thesis is to characterize a representative sample of Supergiant X-ray Binaries (SGXBs) formed by 4 sources: XTE J1855-026, a classical SGXB with long-term stable X-ray flux; AX J1841.0-0535 and AX J1845.0-0433, two supergiant fast X-ray transients (SFXTs) with the X-ray emission mostly dominated by flaring; and IGR J00370+6122, something in between these 2 sub-groups. The physical processes that produce these observable differences are still a matter of debate. In this PhD Thesis I performed a study of these 4 different systems to provide new data to constrain the models. This study consists of:(i) the determination of the orbital solution,(ii) a systematic study of the wind behavior along the orbit by the measure of Halpha variations,(iii) a model of stellar atmospheres of the donor star,(iv) establish whether there are X-ray flux variations modulated by the orbital period. The study of the wind shows that Halpha variations are dominated by intrinsic wind processes. The stellar atmospheres study shows that the supergiant stars that harbor these binaries have a higher projected rotational velocity, higher He abundance and higher N/C ratio than that of isolated supergiant stars. The results of this study show that the eccentricity of the binary does not have a simple correlation with the differences in the X-ray flux of the different sub-groups. Therefore, the idea of a more complex scenario is consolidated. The discovery of a new type of system, IGR J00370+6122, which properties do not fit in any of the established sub-groups, reinforces the idea of a continuum in the observed properties more than a strict classification of systems. Furthermore, I have developed a pipeline to reduce spectra of the FRODOSpec spectrograph at the Liverpool Telescope optimized for the reduction of the red spectra of the obscured supergiants that we find in these SGXBs.

研究动机与目标

• 表征四个大质量X射线双星的轨道与风特性，涵盖经典SGXBs与SFXTs。
• 确定X射线通量变化是否受轨道周期调制，以检验吸积变异性模型。
• 研究供体超巨星的物理特性，特别是其表面成分与自转特性。
• 评估轨道偏心率是否与X射线通量行为相关，以挑战现有分类方案。
• 开发针对SGXB系统中被遮蔽超巨星红波段光谱的专用数据还原处理流程。

提出的方法

• 利用光谱数据中的径向速度测量确定轨道解。
• 系统性监测Halpha线变异性，以追踪轨道周期内风行为与质量损失。
• 对供体恒星进行恒星大气建模，以推导投影自转速度、氦元素丰度及氮碳比。
• 分析X射线光 light curves，检测轨道调制并评估通量变异性模式。
• 开发针对FRODOSpec光谱仪红波段光谱的专用数据还原处理流程，优化用于被遮蔽超巨星的分析。
• 对SFXT与经典SGXB子类系统进行对比分析，以识别趋势与异常现象。

实验结果

研究问题

• RQ1 所研究的四个大质量X射线双星的轨道解与轨道周期是什么？
• RQ2 轨道不同相位的Halpha线变异性如何反映内在风过程，而非外部吸积诱导效应？
• RQ3 供体超巨星的表面成分与自转特性如何？与孤立超巨星相比有何差异？
• RQ4 在子类之间，轨道偏心率与X射线通量变异性是否存在可测量的相关性？
• RQ5 中等性质系统IGR J00370+6122是否代表一个独立类别，还是连续属性分布的一部分？

主要发现

• Halpha变异性主要由内在风过程驱动，而非外部吸积诱导效应。
• 这些系统中供体恒星的投影自转速度更高，氦元素丰度更高，氮碳比也更高，与孤立超巨星相比存在显著差异。
• 轨道偏心率与X射线通量行为之间不存在简单相关性，表明其背后存在更复杂的物理机制。
• IGR J00370+6122的发现表明，该系统不符合既有的SFXT或经典SGXB分类标准，支持系统属性为连续分布而非离散分类群的观点。
• 成功开发了一套针对SGXB系统中被遮蔽超巨星红波段光谱的新型优化数据还原处理流程。
• 本研究强化了大质量X射线双星中吸积变异性由风动力学与恒星特性共同决定的观点，而非仅由轨道几何决定。