Parkes observations for project P456 semester 2019APRS_40

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的认知。PPTA是三大国际脉冲星计时研究组中历史最悠久的一个。尽管我们的望远镜与研究团队规模均为三者中最小，却斩获了最优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观测约束，是目前唯一可有效约束相关理论模型的结果。我们能够始终保持领域领先地位的原因在于：拥有南天区观测视野；拥有一支精干且目标聚焦的研究团队；配备了经过最优校准的接收系统；以及能够以15至20天的近乎规则周期开展宽频带观测。通过本观测申请，我们旨在维持在该领域的领先地位。与多数观测申请不同，本申请属于持续性观测项目，其观测工作将持续优化超低频引力波的约束精度，直至最终成功探测到该引力波背景。帕克斯望远镜的持续观测至少仍将具备重要科学价值，直至平方千米阵列（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。即便在引力波背景被成功探测之后，我们仍需持续开展观测，以支撑这一新兴的引力波天文学领域的发展！