Parkes observations for project P456 semester 2018APRS_20

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.

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）探测来自天文源的引力波（gravitational waves），（b）建立脉冲星时标系统（pulsar timescale），（c）深化对太阳系动力学（Solar-system dynamics）的认知。PPTA是三大国际脉冲星计时团队中历史最悠久的一支。尽管我们拥有的望远镜与团队规模均为三者中最小，但却取得了最优的测量结果与科研成果。我们针对非相干引力波背景（incoherent gravitational wave background）强度给出的约束，是目前唯一能显著约束相关理论模型的限制条件。我们能够始终保持领先地位的原因在于：我们坐拥南天球观测天区；拥有一支精干且目标高度聚焦的团队；配备了校准精度最高的接收机；并且能够以15至20天的近乎规律观测周期，在三个不同波段开展观测。通过本申请，我们旨在维持本领域的领先地位。

与大多数观测申请不同，本申请属于持续性项目，相关观测将持续优化超低频引力波（ultra-low-frequency gravitational waves）的约束精度，直至最终直接探测到这类引力波。帕克斯天文台的持续观测至少将在平方千米阵列（Square Kilometre Array, SKA）第一阶段项目实现灵敏度与观测频次的提升之前，始终具备科研价值。即便在引力波背景被成功探测之后，我们仍将持续开展观测，以支撑这一新兴的引力波天文学（gravitational wave astronomy）领域发展！