Long-term project observations for project P456 semester 2025APRS_10

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) 建立脉冲星时标系统；(c) 加深我们对太阳系动力学的认知。目前我们正处于一个令人振奋的研究阶段：本项目（及其他相关数据集）中探测到的信号，与引力波背景的理论预期特征高度吻合。当前我们正联合国际学界全力开展工作，以验证或推翻该探测结果，并厘清该信号的天体物理起源。依托本次观测申请，我们旨在巩固本领域的领先地位。本项目为持续性观测申请，将持续对毫秒脉冲星（millisecond pulsars, MSPs）开展观测，以不断收紧超低频率引力波的探测限值，直至我们能够以高置信度确认其存在。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）一期工程能够提升我们的观测灵敏度与观测时序。即便引力波背景已被成功探测，持续开展的观测仍将厘清该背景的起源，并甄别出单个引力波源，进而推动引力波天文学这一新兴领域的发展。