Parkes observations for project P456 semester 2019APRS_21

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）项目设有三大核心目标：（a）探测来自天文天体的引力波，（b）建立脉冲星时标系统，（c）深化对太阳系动力学机制的理解。PPTA是三大国际脉冲星计时合作组中历史最为悠久的一个。尽管我们的望远镜与团队规模均为三者中最小，却取得了最优的观测精度与科研成果。我们给出的非相干引力波背景强度约束，是目前唯一能够显著约束相关理论模型的定量结果。我们始终保持领域领先地位的原因在于：坐拥南天球观测视野；拥有一支精干且目标高度聚焦的团队；配备了校准精度顶尖的接收系统；并且能够以15至20天的近乎稳定观测周期，在宽带宽范围内开展持续观测。本提案旨在维系我们在该领域的领军地位。

与绝大多数观测提案不同，本提案属于持续性观测项目，相关观测将持续优化超低频率引力波的约束精度，直至最终探测到这类引力波。帕克斯（Parkes）望远镜的持续观测至少仍将保有重要科研价值，直至平方公里阵列（Square Kilometre Array, SKA）的第一阶段项目能够在灵敏度与观测节奏上超越我们。即便在引力波背景被成功探测之后，我们仍将继续开展观测，以支撑新兴的引力波天文学领域的发展！