Parkes observations for project P1162 semester 2023OCTS_08

Pulsar timing is a powerful tool in studying pulsar physics. Discovering more exotic pulsar systems or timing pulsars with higher precision is an essential part of pulsar astronomy. As a recently discovered millisecond pulsar, PSR J1402+13 is an interesting source for follow-up timing observations. First, its apparent spin-down rate, as reported in the catalogue, was the highest among known millisecond pulsars, causing a seeming tension with the spin-up theory. Second, its apparent high flux density and small distance seemed to give a high timing precision. We have observed J1402+13 with high cadence in the past 9 months and obtained a phase-coherent solution, which gives a much lower pdot (~ 10^{-20} s/s) thus solves the tension with the spin-up theory. We apply for another 15 hours to observe the pulsar to further extend the timing baseline, which will refine our timing solution and help us clearly evaluate its timing precision and potential to be used for pulsar timing arrays. The observation will also help us study the scintillation effect of the pulsar and measure its steep spectral index. The more comprehensive measurements of the pulsar will also facilitate observations in optical and gamma-ray bands.

脉冲星计时（pulsar timing）是研究脉冲星物理的有力工具。发现更多奇异脉冲星系统或以更高精度开展脉冲星计时观测，是脉冲星天文学的核心任务之一。PSR J1402+13作为近期发现的毫秒脉冲星，是后续计时观测的重要目标。首先，其表观光自旋减慢率（apparent spin-down rate）在已知毫秒脉冲星中居首，与自旋加速理论（spin-up theory）存在明显冲突；其次，其表观高通量密度（flux density）与较近距离的特性，有望实现高精度计时。过去9个月，我们对J1402+13开展了高采样率观测，获得了相位相干解（phase-coherent solution），其自旋减慢率（pdot）显著降低（约10^-20 s/s），从而解决了与自旋加速理论的矛盾。我们申请额外15小时观测时间，以进一步延长计时基线（timing baseline），优化计时解，并明确评估其计时精度及作为脉冲星计时阵列（pulsar timing arrays）成员的潜力。此外，该观测还将助力研究脉冲星的闪烁效应（scintillation effect）、测量其陡峭光谱指数（spectral index），并为光学与伽马射线波段的观测提供支撑。