Parkes observations for project P456 semester 2018OCTS_33

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 at three different wavelengths. 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）项目确立了三大核心科研目标：(a) 探测天文源产生的引力波；(b) 建立标准化脉冲星时标体系；(c) 深化对太阳系动力学的认知。该阵列是全球三大国际脉冲星计时研究组中历史最悠久的一支。我们虽拥有规模最小的望远镜与科研团队，却取得了精度最高的观测数据与最优异的科研成果。我们针对非相干引力波背景强度给出的约束，是目前唯一能对相关理论模型构成显著限制的约束结果。我们能始终保持该领域领先地位的原因在于：我们占据南天天区的观测优势；拥有一支精干且目标高度聚焦的团队；配备了经过最精密校准的射电接收机；并且能够以15至20天的近乎恒定观测周期，在三个不同波段开展持续观测。通过本提案，我们旨在维持自身在该研究领域的领先地位。

与绝大多数观测提案不同，本提案属于持续性观测项目，相关观测工作将持续优化对超低频引力波的约束精度，直至最终实现引力波的直接探测。帕克斯望远镜的持续观测至少在平方千米阵列（Square Kilometre Array, SKA）第一阶段能够实现优于我们的观测灵敏度与观测周期之前，仍将具备极高的科研价值。即便引力波背景被成功探测，我们仍需持续开展观测，以支撑新兴的引力波天文学领域的发展！