脉冲星磁层中共振逆康普顿散射对次级粒子分布函数的影响

共振逆康普顿散射(RICS)已被证明在典型的脉冲星表面温度和磁场条件下,是次级粒子(洛仑兹因子低于104)主要的能量损失机制.次级粒子的分布函数也会因为共振逆康普顿而改变.文章重新计算了次级粒子最后稳定分布函数,并修正了Lyubarskii和Petrova(2000)一文中分布函数结果不满足次级粒子数目守恒的假设.就此结果在解释脉冲星射电谱拐折现象中的应用进行了讨论.     

脉冲星在磁偶极辐射作用下自转周期和周期变率随年龄的演变

对脉冲星由于磁辐射使自转周期和周期变率随年龄的演变做了进一步深入研究，给出了适合用观测值计算的理论式子，并用它对四颗脉冲星的自转周期和周期变率随年龄演变情况做了数值计算，绘出了演变曲线。结果表明，四颗脉冲星的自转周期皆随年龄的增加而延长，但周期变率皆随年龄的增加而增少。     

基于单探测器的低轨航天器X射线脉冲星导航算法

近年来脉冲星自主导航技术飞速发展,即将在低轨道(LEO)航天器开展验证。为了适应低轨航天器载荷轻量化、小型化的需求,研究了基于单探测器的X射线脉冲星导航扩展卡尔曼滤波算法,并针对单脉冲星导航和轮流观测多脉冲星导航两种方案,分别进行了算法仿真。仿真结果表明,仅观测单脉冲星无法实现长期自主导航,但能够将轨道预报误差降低25.9%,提高短期自主导航精度。而单探测器轮流观测多脉冲星可实现长期自主导航,其导航误差达到514 m,与多探测器同时观测多脉冲星传统算法相当。     

中心有脉冲星的︽暴970228火球模型

重点讨论了中心有脉冲星的γ射线暴火球模型,假定在火球的中心有一强磁场的毫秒级脉冲星,改变以往文献中的能量转化方程,计算出GRB970228的辐射流,与观测结果符合的很好.自然解释了GRB970228余辉的光变曲线特征.     

Pulsar observations in China

The development history and achievement of pulsar observation in China were introduced. The history is very short, only ten years. The cooperation program about pulsar timing observation at 18 cm using a 25-m radio telescope of UAO between China, Australia and Great Britain has been carried out since 1997. Some scientific results such as glitch, model changing, interstellar scintillation and the spectra of pulsar have been obtained. The plans of development of the pulsar observation were also introduced using Chinese radio telescopes.     

中子星辐射引力红移的量子真空极化修正

测量中子星表面辐射谱的引力红移被认为是探究这类致密天体基本物理特性最为直接有效的手段. 但是,脉冲星、磁星这些强磁化中子星表面的辐射红移不仅源于引力的作用, 还需要考虑星体表面的磁化等离子体以及由超强磁场所诱导的量子电动力学(quantum electrodynamics, QED) 真空极化效应对辐射的电磁作用. 运用Gordon有效度规理论研究磁化等离子体以及QED真空极化效应对星体辐射的影响. 计算结果表明, 一般情况下对辐射引力红移的修正起主要作用的是星体表面的磁化等离子体, 但在某些特定情况下, 还必须考虑QED真空极化效应的作用.     

基于脉冲星相关的编队航天器间相对距离的确定

针对编队航天器间相对导航的需要,提出了利用脉冲星的脉冲接收信息确定编队航天器间相对距离的方法。该方法利用编队航天器对同一脉冲星的观测信息,将不同航天器接收的脉冲星信号进行相关处理而获得航天器间相对距离。同时通过对脉冲星频谱特征的分析,给出了相对距离估计的精度。结合实际的编队航天器系统的轨道信息进行了仿真,结果表明,利用相关估计的方法可以完成航天器间的相对距离确定,为今后航天器编队飞行的应用提供了新的技术支持。     

X-ray pulsar signal detection using photon interarrival time

The distribution probability of the photon interarrival time （PIT） without signal initial phases is derived based on the Poisson model of X-ray pulsar signals, and a pulsar signal detection algorithm employing the PIT sequence is put forward. The joint probability of the PIT sequence is regarded as a function of the distribution probability and used to compare a constant radiation intensity model with the nonhomogeneous Poisson model for the signal detection. The relationship between the number of detected photons and the probabilities of false negative and positive is studied, and the success rate and mean detection time are estimated based on the number of the given photons. For the spacecraft velocity data detection, the changes of time of photon arrival （TOPA） and PIT caused by spacecraft motion are presented first, then the influences on detection are analyzed respectively. By using the analytical pulse profile of PSR B0531＋21, the simulation of the Xray pulsar signal detection is implemented. The simulation results verify the effectiveness of the proposed method, and the contrast tests show that the proposed method is suitable for the spacecraft velocity data detection.     

脉冲星信号的模糊阈值小波降噪算法

为了提高脉冲星辐射脉冲信号的信噪比,提出了基于模糊阈值的小波降噪算法.该算法的核心思想为:引入模糊理论,通过建立隶属度函数,计算出每个采样点信号幅值的隶属度,再利用小波阈值消噪的方法设定门限来分析隶属度,将隶属度大于门限的采样值划归为信号,反之为噪声,从而达到压抑噪声、保留信号的目的.实验结果表明,与基于极大极小原理和Stein无偏似然原理的降噪方法相比,基于模糊阈值的小波降噪算法将脉冲信号的信噪比提高了大约5~6 dB,同时可以保留信号的细节.新算法为脉冲星信号处理与应用提供了一个行之有效的算法.