Long-term project observations for project P456 semester 2025OCTS_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. We are now in an exciting regime where a signal detected in our (and other data sets) has the form expected for a gravitational wave background. We, along with the international community, are now working hard to either confirm or deny this result, and to determine the astrophysical origin of this signal. With this proposal, we aim to maintain our pre-eminent position in the field. This is a continuing proposal for which observations of millisecond pulsars (MSPs) will continue to improve bounds on ultra-low-frequency gravitational waves until they are detected with confidence. 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, continued observations will resolve the background origin and individual sources will be identified; advancing 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) 探测来自天文天体的引力波，(b) 建立标准化脉冲星时标系统，(c) 深化对太阳系动力学的认知。当前我们正处于令人振奋的研究阶段——我们（及其他相关数据集）中探测到的信号，其形态完全符合引力波背景的预期特征。目前我们与国际学界正通力协作，旨在证实或证伪这一观测结果，并厘清该信号的天体物理起源。通过本项目提案，我们旨在巩固自身在该领域的领先地位。本项目为持续性观测项目，将通过对毫秒脉冲星（millisecond pulsars, MSPs）的持续观测，不断收紧超低频引力波的参数约束，直至我们能够以高置信度实现这类信号的确定性探测。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全面提升我们的探测灵敏度与观测节奏。即便引力波背景被成功探测，持续的观测仍将解析该背景的物理起源，并识别出单个引力波源；这将推动尚处萌芽阶段的引力波天文学领域实现跨越式发展。