极端致密脉冲双星光学对应体的搜寻证认

Due to the extreme stability of its spin period, the pulsar’s radio pulse timing can be a good approach to the detection of the gravitational waves and the spacecraft navigation. However, the pulsar’s time of arrival (TOA) is not exactly accurate. There are two types of timing residuals of the TOA, the glitch with the short time scale and the significant variability, and the long-periodic timing noise that changes slowly. The ultra-compact binary model comes up with two mechanisms to explain the various characteristics of the pulsar timing residual, the Doppler residual and the geodetic precession. The model predicts that the quasi-periodic feature of 1-10 years in pulsar timing residual corresponds to an ultra-compact binary with the orbital period of 1-25 minutes. At the end of 2014, we observed the continuous single pulse sequences of sevaral ultra-compact binary candidates using Arecibo telescope. The preliminary analysis of the the single pulse data supports the ultra-compact binary model. Based on the ultra-compact binary model, this project aims to search for the optical counterparts of ultra-compact binary candidates and identify the white dwarf nature of the pulsars’ companions. We will use the optical observations to find the white dwarf companions of the binary candidates. The binary orbital parameters will be derived by the analysis of the photometric and spectroscopic data. The result of the project will provide strong evidence for the ultra-compact model and of great help to improve the ultra-compact binary model. The verification of the ultra-compact binary model will be an important approach to solve the problem of the pulsar timing noise.

脉冲星自转周期的稳定性，使其射电脉冲在时间测量方面有重要的应用前景。脉冲星的脉冲到达时间存在着时间残差——短时标突变的glitch和长时标缓变的时间噪声。解决脉冲星的时间残差问题对脉冲星物理和脉冲星的测时应用具有突破性的意义。极端致密双星模型可成功解释不同类型的脉冲星时间噪声。针对时间噪声长达1-10年准周期特征的脉冲星，该模型预言轨道周期为1-25分钟的极端致密脉冲双星的存在。2014年底，使用Arecibo射电望远镜对几颗极端致密脉冲双星候选体进行的持续单脉冲观测数据的初步分析结果为此双星模型提供了支持。本项目以极端致密双星模型为基础，搜寻证认极端致密脉冲双星的光学对应体。具体内容包括：对脉冲双星候选体进行光学观测，寻找和证认其光学对应体的恒星类型；根据观测获得的运动学信息，计算双星系统的轨道参数，完善极端致密双星模型。本项目旨在为极端致密双星模型提供直接证据，解决脉冲星时间噪声问题。

由于原项目计划的实施遇到了困难，本项目的工作内容进行了相应的调整，改为对测时数据具有特殊性质的脉冲星的测时特性的产生原理及应用。主要内容包括：极端致密脉冲双星候选体PSR 0919+06的光学对应体的搜寻和证认，用蟹状星云脉冲星的多波段测时数据检验弱等效原理，用回落盘进动模型解释毫秒脉冲星J0437-4715的时间噪声。本项目的研究工作一方面拓展了脉冲星测时特性的应用，另一方面为毫秒脉冲星的脉冲稳定性的改进提供了新的解决途径。