Parkes observations for project P456 semester 2018APRS_30

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）项目拥有三大核心目标：(a) 探测来自天文源的引力波；(b) 建立标准化脉冲星时标；(c) 深化对太阳系动力学机制的认知。PPTA是全球三大国际脉冲星计时合作团队中历史最悠久的一支。尽管我们拥有规模最小的望远镜阵列与研究团队，但却产出了质量最优的观测数据与最具影响力的研究成果。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形成有效限制的观测约束。我们能始终保持领域领先地位的原因在于：我们坐拥南天穹顶的独特观测视野；拥有一支规模小巧但目标高度聚焦的研究团队；配备了经过最精准校准的接收机系统；并且能够以每15至20天近乎规律的周期在三个不同观测波段开展持续观测。通过本提案，我们旨在巩固自身在该领域的领军地位。与多数观测提案不同，本提案属于持续性观测项目，相关观测将持续优化对极低频引力波的约束精度，直至最终实现此类引力波的直接探测。帕克斯望远镜的持续观测至少仍将具备重要科学价值，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观测周期上超越我们。即便引力波背景被成功探测，我们仍需持续开展观测，以支持这一新兴的引力波天文学领域的发展！