基于慧眼卫星的极亮 X 射线脉冲星 Swift J0243.6+6124 的辐射特征研究

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	基于慧眼卫星的极亮 X 射线脉冲星 Swift J0243.6+6124 的辐射特征研究
其他题名	Study of radiative properties of the ultraluminous X-ray pulsar Swift J0243.6+6124 with Insight-HXMT
	赵庆霞
学位类型	硕士
导师	王建成 ; 侯贤
	2024-07-01
学位授予单位	中国科学院大学
学位授予地点	北京
学位专业	天体物理
关键词	Swift J0243.6+6124 中子星 X 射线双星吸积脉冲星极亮 X 射线源
摘要	X射线双星是由一颗致密星（中子星或黑洞）与一颗伴星（恒星）所组成的系统，是天空中最亮的一类X射线源。致密星从伴星吸积物质，通过释放引力势能产生X射线辐射。极亮X射线源（Ultraluminous X-ray sources ，ULXs）是视光度（假设各向同性）超过1039 erg s-1的一类X射线源，超过了质量小于10 倍太阳质量的黑洞的爱丁顿光度。2014年从ULX M82 X-2探测到了连续的脉冲辐射，说明其中心引擎是强磁场中子星，被称为极亮X射线脉冲星（Pulsating Ultraluminous X-ray sources, PULXs）。目前已发现12颗PULXs，它们超高的光度为研究磁化中子星的超爱丁顿吸积提供了一个独特的机会。慧眼（Insight-HXMT）卫星是中国第一颗X射线天文卫星，具有大有效面积、观测能段更宽和更高（1-250 keV）的优势，为研究X射线双星的高能辐射性质提供了独特的机会。尤其是在高能段，慧眼卫星是目前唯一可以进行超过100 keV脉冲能量搜索的在轨卫星。 X射线吸积脉冲星Swift J0243.6+6124在2017-2018年的大爆发中峰值光度达到2×1039 erg s-1，是银河系内第一颗、也是目前发现的唯一一颗PULX。我们利用慧眼卫星对Swift J0243.6+6124在2017-2018年大爆发的宽能段观测，用自发展的交叉相关方法探测到了其超过200 keV的脉冲辐射，这是迄今为止从PULXs观测到的最高脉冲能量。我们还获得了爆发期间每个曝光号的最高脉冲能量，发现最高脉冲能量与光度大体上呈正相关。最后，我们发展了一种新的确定临界光度的方法，当高低能主脉冲相位一致时，即认为发生了由铅笔型模式主导到风扇型模式主导的辐射模式的转变，此时的光度即为临界光度。利用此方法，我们认证出Swift J0243.6+6124的临界光度约为4×1038 erg s-1，与通过能谱分析得到的结果一致。由此估算的磁场与利用回旋吸收线估算的磁场接近，表明该源很可能具有多极的表面磁场，而非偶极场。我们还发现在临界光度之上，所有能段主峰的相位逐渐从0.5移动到0.8，这与前人工作中在低能段下发现的相位差一致。这是首次在高能段观测到类似的现象。本文发展的通过探测最高脉冲能量和比较高低能脉冲相位来确定临界光度的方法充分利用了慧眼在高能段独一无二的优势。该方法模型依赖度小，更具有普遍性，为更好地利用临界光度来估算中子星磁场提供了一种新的思路。
其他摘要	X-ray binaries are systems composed of a compact object (neutron star or black hole) and a companion star. They are the brightest X -ray sources in the sky. The compact object accrets material from the companion and generates X-ray radiation by releasing the gravitational potential energy. Ultraluminous X-ray sources (ULXS) are astrophysical objects with apparent X-ray luminosity (assuming isotropic emission) exceeding 1039 erg s-1, above the Eddington limit for a stellar-mass black hole with less than 10 solar masses. In 2014, pulsed emission was detected from the ULX M82 X-2, indicating that the central engine is a strongly magnetized neutron star, and is then known as the Pulsating Ultraluminoot X-Ray Source (PULX). Up to now, 12 PULXs have been detected, and their ultra-high luminosity provides a unique opportunity for studying the super-Eddington accretion of magnetized neutron stars.Insight-HXMT is the first X-ray astronomical satellite of China. It has the advantages of large effective area, larger and higher energy range (1-250 keV), providing a unique opportunity for studying the high-energy radiation properties of X-ray binaries. Especially, HXMT is currently the only on-orbit satellite that can measure pulse energies exceeding 100 keV.Swift J0243.6+6124 is the first and only PULX in the Milky Way that is currently discovered. During its 2017-2018 outburst, its luminosity reached 2×1039 erg s-1. Owing to the broad-band observation of Insight-HXMT and using our newly developed cross-correlation method, we have detected the highest energy of pulsation exceeding 200 keV from Swift J0243.6+6124, which is the highest energy detected from PULXs to date. We also obtained the highest energy of pulsation of every exposure during the 2017-2018 outburst, and found that the highest energy is roughly positively correlated with luminosity. Finally, we have developed a new method to determine the critical luminosity, which separates the fan-beam dominated and pencil-beam dominated accretion regimes. By examining at what luminosity the low energy pulse peak becomes aligned with the high energy pulse peak, we identified the critical luminosity to be about 4×1038 erg s-1. Our result is consistent with what was derived from spectral analysis. The magnetic field thus estimated is close to that obtained using cyclotron absorption lines, indicating that the source is likely to have a multipole surface magnetic field rather than a dipole field. We also found that above the critical luminosity, the phase of the main peak shifted gradually from 0.5 to 0.8 in all energy bands, in agreement with the phase shift found previously at lower energies. This is the first time that a similar phenomenon has been observed in higher energy bands for this source.The method developed in this work to determine the critical luminosity by detecting the highest energy pulsation and comparing the phases of high and low energy main pulse profiles takes the unique advantages of Insight-HXMT in the high energy range. This method has less model dependence and is thus more universal, providing a new idea to better utilize critical luminosity to estimate the magnetic fields of neutron stars.
学科领域	天文学
学科门类	理学 ; 理学::天文学
页数	0
语种	中文
文献类型	学位论文
条目标识符	http://ir.ynao.ac.cn/handle/114a53/28028
专题	星系类星体研究组
作者单位	中国科学院云南天文台
第一作者单位	中国科学院云南天文台
推荐引用方式 GB/T 7714	赵庆霞. 基于慧眼卫星的极亮 X 射线脉冲星 Swift J0243.6+6124 的辐射特征研究[D]. 北京. 中国科学院大学,2024.

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