Parkes observations for project P1162 semester 2023OCTS_09

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）是研究脉冲星物理学的强有力工具。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，是脉冲星天文学研究的核心内容之一。作为近年发现的毫秒脉冲星（millisecond pulsar），PSR J1402+13是后续计时观测的极具研究价值的源。其一，该源在星表中记录的视自转减慢率（spin-down rate）为已知毫秒脉冲星中最高，看似与自转加速理论（spin-up theory）存在矛盾；其二，其视流量密度较高且距离较近，理论上应具备较高的计时精度。我们在过去9个月内以高频观测节奏对J1402+13开展了观测，并获得了相位相干解（phase-coherent solution），得到了远更低的自转周期变化率（pdot，约10^{-20} s/s），从而解决了与自转加速理论的矛盾。我们申请额外15小时观测时长以开展该脉冲星的后续观测，进一步延长计时基线，这将优化我们的计时解算结果，帮助我们明确评估其计时精度，以及其在脉冲星计时阵列（pulsar timing arrays）中的应用潜力。本次观测还将助力我们研究该脉冲星的星际闪烁效应，并测量其陡谱指数。对该脉冲星更全面的观测测量，也将为光学与伽马射线波段的后续观测提供支撑。