Parkes observations for project P456 semester 2018APRS_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 at three different wavelengths. With this proposal we aim to maintain our pre-eminent position in the field.\r\n\r\nUnlike 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）探测源自天文天体的引力波，（b）建立脉冲星时标体系，（c）深化对太阳系动力学的认知。PPTA是全球三大国际脉冲星计时研究团队中历史最悠久的一个。尽管我们拥有的望远镜与研究团队规模均为三者中最小，却取得了最精准的观测数据与最出色的研究成果。我们针对非相干引力波背景强度所设定的约束条件，是目前唯一能够显著限制相关理论模型的约束成果。我们能够始终保持领先地位的原因在于：坐拥南天空域的观测优势；拥有一支精干且聚焦的研究团队；配备了经过最优校准的接收机；并且能够以每15至20天近乎规律的观测节奏，在三个不同波段开展观测。本次提案旨在巩固我们在该领域的领先地位。

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，直至最终成功探测到这类引力波。帕克斯天文台的持续观测仍将具备重要科学价值，至少要等到平方千米阵（Square Kilometre Array, SKA）第一阶段项目能够在观测灵敏度与节奏上超越我们当前的水平。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工作，以支撑这一新兴的引力波天文学领域的发展。