基于IPTA数据的毫秒脉冲星综合稳定度评估

利用脉冲星极其稳定的自转频率可以形成一种天文时间基准，部分毫秒级脉冲星的稳定度甚至超越了原子钟，但其观测稳定度易受多种噪声源的影响。一般来说，不同的脉冲星的噪声大部分是相互独立的，因此可以通过加权综合和滤波算法构建综合脉冲星时，有效去除计时残差中的噪声。针对此问题，采用10颗毫秒级脉冲星的国际脉冲星计时阵列（international pulsar timing array, IPTA）数据进行了稳定度评估分析，其中7颗脉冲星的观测数据长度在10年以上。综合考虑单颗脉冲星稳定度评估的结果和观测数据的长度后，筛选出了4颗脉冲星用于构建综合脉冲星时。同时对比了经典加权算法、小波分解算法和维纳滤波算法的综合脉冲星时稳定度结果。结果表明：脉冲星的长期稳定度优于短期稳定度，2颗脉冲星在1年处稳定度达10-15量级，8颗在1 000天处也达到了10-15量级，其中PSR J1600-3053在5年处稳定度达到了最佳，为7.023×10-16 。此外，三种算法中，维纳滤波建立的综合脉冲星时稳定度最佳，在5年处达到了1.502×10-15，优于参与构建的其他所有脉冲星的5年稳定度。

Ensemble stability estimate of millisecond pulsars using IPTA observations

Utilizing the highly stable rotational frequencies of pulsars can establish an astronomical time reference. In fact, the stability of some millisecond pulsars surpasses that of atomic clocks. However, the observed stability of pulsars is susceptible to various sources of noise. Generally, the noise in different pulsars is mostly independent, allowing for the effective removal of the noise in timing residuals through weighted synthesis and filtering algorithms when constructing pulsar timing arrays. In addressing this issue, an estimation of stability is conducted using data from the international pulsar timing array (IPTA), comprising observations from 10 millisecond pulsars, with 7 of them having data spanning over a decade. Combining the individual timing stability estimation with the lengths of the observation data, 4 pulsars are selected for the synthesis of a pulsar timing array. Furthermore, a comparison is made among the results of classical weighting algorithms, wavelet decomposition algorithms, and Wiener filtering algorithms in terms of the stability of the ensemble pulsar timing. The findings reveal that long-term stability of pulsars exceeds their short-term stability. The stability of two pulsars reaches the level of 10-15 at 1 year, and eight of them achieve this level at 1 000 days. Notably, PSR J1600-3053 exhibits the best stability at 5 years, with a value of 7.023×10-16. Additionally, among the three algorithms, the ensemble pulsar time provided by the Wiener filter shows the best stability, reaching 1.502×10-15 at 5 years, surpassing the 5-year stability of all other constructed pulsars.