Parkes observations for project P456 semester 2019APRS_50

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）项目共有三大核心目标：（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机制的认知。帕克斯脉冲星计时阵列是三大国际脉冲星计时研究群组中历史最悠久的一员。尽管我们拥有规模最小的望远镜系统与最精简的研究团队，但却斩获了最精准的观测数据与最卓越的研究成果。我们针对非相干引力波背景强度给出的约束条件，是目前唯一能显著限制相关理论模型的观测约束。我们能够始终保持领域领先地位的原因在于：其一，我们坐拥南天星空的观测优势；其二，团队规模虽小但研究方向高度聚焦；其三，配备了校准精度最优的接收机；其四，能够以近乎规则的15至20天观测间隔在宽带宽范围内开展持续观测。藉由本次提案，我们旨在巩固并维持本领域的领先地位。与多数观测提案不同，本次提案属于持续性观测项目，其观测工作将持续约束超低频率引力波的探测边界，直至最终成功直接探测到这类引力波。帕克斯望远镜的持续观测至少在平方公里阵列（Square Kilometre Array，SKA）第一阶段项目实现灵敏度与观测频次的优化之前，仍将具备极高的科研价值。即便引力波背景被成功探测，我们仍将持续开展观测，以支持这一新兴的引力波天文学领域的发展！