Parkes observations for project P456 semester 2019OCTS_07

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!

Parkes脉冲星计时阵列（Parkes Pulsar Timing Array, PPTA）项目拥有三大核心目标：（a）探测来自各类天体源的引力波；（b）建立标准化脉冲星时标系统；（c）深化我们对太阳系动力学机制的理解。PPTA是全球三大国际脉冲星计时合作团队中历史最为悠久的一支。尽管我们配备的望远镜与团队规模均为三者中最小，却斩获了目前最优质的观测数据与研究成果。我们针对非相干引力波背景强度给出的约束条件，是当前唯一能够显著限制相关理论模型的约束结果。本团队能够长期保持领域领先地位的原因在于：坐拥南天区得天独厚的观测空域；拥有一支精干且目标高度聚焦的科研团队；配备了校准精度顶尖的接收机；且能够以15至20天的近乎恒定观测周期开展宽带宽观测。本提案旨在维系我们在该研究领域的领军地位。与绝大多数观测提案不同，本提案属于持续性观测项目，其积累的观测数据将持续收紧对极低频引力波的约束强度，直至最终实现该信号的直接探测。帕克斯天文台的持续观测至少将在平方千米阵列（Square Kilometre Array, SKA）第一阶段完成灵敏度与观测节奏升级之前，持续保有其科研价值。即便引力波背景被成功探测，我们仍需持续开展观测，以支撑引力波天文学这一新兴研究领域的发展。