Parkes observations for project P456 semester 2020APRS_14

The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. The PPTA is the oldest of three international pulsar timing groups. We have the smallest telescope and the smallest group, but the best measurements and the best results. Our bound on the strength of the incoherent gravitational wave background is the only bound which significantly constrains theoretical models. We have maintained our leading position because: we have the southern sky; we have a small but well-focussed group; we have the best-calibrated receivers; and we have been able to observe with an almost regular cadence of 15 to 20 days over a wide bandwidth. With this proposal we aim to maintain our pre-eminent position in the field. Unlike most observing proposals, this is a continuing proposal for which the observations will continue to improve bounds on ultra-low-frequency gravitational waves until they are finally detected. Continued Parkes observations will remain valuable at least until the first stage of the SKA is able to improve on our sensitivity and observing cadence. Even after the gravitational wave background is detected we will want to continue observations in support of the nascent field of gravitational wave astronomy!

帕克斯脉冲星计时阵列（Parkes Pulsar Timing Array, PPTA）项目设有三大核心目标：（a）探测来自天文源的引力波；（b）建立脉冲星时标系统；（c）深化对太阳系动力学的认知。PPTA是三大国际脉冲星计时研究团队中历史最悠久的一支。尽管我们的望远镜与研究团队规模均为三者之最，但却拥有最精良的观测数据与最顶尖的研究成果。我们针对非相干引力波背景强度给出的约束条件，是目前唯一可对相关理论模型形成有效限制的约束。我们能够长期保持领域领先地位的原因在于：我们坐拥南半球天空的观测优势；拥有一支规模小巧但目标高度聚焦的研究团队；配备了校准精度最高的接收机；并且能够以15至20天的近乎恒定观测周期，在宽带宽范围内开展持续观测。藉由本次提案，我们旨在巩固本领域的领先地位。与绝大多数观测提案不同，本次提案属于持续性观测项目，其观测工作将持续优化极低频引力波的约束精度，直至最终实现该信号的直接探测。帕克斯望远镜的持续观测至少仍将保有重要科学价值，直至平方公里阵列（Square Kilometre Array, SKA）的第一阶段项目能够在观测灵敏度与周期上超越我们。即便引力波背景被成功探测，我们仍需持续开展观测，以支撑刚刚兴起的引力波天文学这一新兴研究领域！