基于射电实测数据研究脉冲星计时误差

Pulsars have very high rotation stability, and are regarded as the most stable "natural clocks". Especially for the millisecond pulsars, the rotation stability could reach 10E-20. Pulsar timing is the foundation of pulsar research, and has a broad prospects of application, such as studing pulsar intrinsic characteristics (rotation parameters, astrometric parameter), giving stringent tests of the general theory of relativity, revealing dispersion measure variations due to the interstellar medium, establishling pulsar time standard, testing the solar system planets ephemeris error, detecting gravitational waves background, etc. Therefore, it is quite necessary to analyze the pulsar timing results with high precision and study all kinds of errors in the processes of pulsar timing. Pulsar timing errors are mainly from three aspects: 1.the pulsar timing observation error; 2.the transform error of the time of arrivals (TOA); 3.the intrinsic noises of pulsars. This project mainly studies the three kinds of errors using the real observing data, gives full analyses of the observing error sources, the influences of the pulsar parameter errors on the TOA transform, and the quantitative errors，and study pulsar timing noise. Due to the studies of this project, one can have a deep understanding of the pulsar timing error sources. Moreover, it can provide theoretical bases for the establishment of the scheme of pulsar timing observations, obtaining the required target of pulsar timing accuracy.

脉冲星具有很高的自转稳定性，被誉为自然界最稳定的“天然钟”。尤其是毫秒脉冲星其自转稳定度高达1.0E-20。脉冲星计时分析是脉冲星研究的基石，可用于研究脉冲星的本征特性（自转参数、位置参数）、检验广义相对论、研究星际介质色散量DM的变化、建立脉冲星时间标准、检测太阳系行星历表误差、探测引力波背景等，具有广泛的应用前景。因而分析高精度的脉冲星计时结果，研究脉冲星计时过程中各种误差影响大小很有必要。 脉冲星计时误差主要来源于三个方面：1.脉冲星计时观测误差；2.到达时间(TOA)转换的误差；3.脉冲星本身内部噪声。本项目利用射电实测数据研究三种误差源，全面分析观测误差来源以及脉冲星参数误差对TOA转换的影响，定量给出误差源大小，详细研究分析脉冲星计时噪声。通过本项目的研究深入了解到脉冲星计时误差来源，为脉冲星计时观测方案的制定提供理论依据，达到提高脉冲星计时精度目标。

脉冲星计时分析是整个脉冲星研究的基石，计时研究及其应用都需要高精度的脉冲星计时分析结果。分析脉冲星计时过程中各种误差源的影响很有必要，有助于根据误差源特性合理制定脉冲星计时观测方案，提高脉冲星计时精度，从而更有助于深入开展脉冲星计时在天体物理及其应用方面的研究工作。本项目利用目前国际上观测精度最高PPTA原始观测数据开展相关研究，通过对原始数据的数据处理详详细分析了部分误差源，主要分析了观测站参考时钟误差、脉冲星位置误差、行星误差、视差误差、不同参考太阳系行星历表等对计时的影响。并定量给出影响大小；另外，利用实测数据分析了VLBI和脉冲星计时给出的位置差异，并详细讨论了两种参考给出的脉冲星天体测量参数对计时结果的影响；最后，利用中科院国家授时中心昊平40米射电望远镜平台，优选部分辐射强的脉冲星开展单脉冲及计时观测研究，并成功探测到多颗脉冲星的单脉冲辐射。