Parkes observations for project P456 semester 2020APRS_06

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!

Parkes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）深化对太阳系动力学的认知。PPTA是三大国际脉冲星计时合作组中历史最悠久的一个。我们的望远镜与团队体量均为三者中最小，但却取得了精度最高的测量结果与最出色的科研成果。我们针对非相干引力波背景强度给出的观测约束，是目前唯一能够显著限制相关理论模型的约束条件。我们能始终保持领军地位的原因在于：坐拥南半球观测天区；拥有一支精干且目标高度聚焦的团队；配备了经过最优校准的接收系统；并且能够以近乎固定的15至20天观测周期，在宽带宽范围内开展观测。本申请旨在维持我们在该领域的领先地位。与绝大多数观测申请不同，本申请属于持续性观测项目，相关观测将持续优化对超低频引力波的约束强度，直至最终直接探测到这类引力波。帕克斯（Parkes）望远镜的持续观测至少将在平方公里阵列（Square Kilometre Array, SKA）第一阶段设备实现灵敏度与观测周期优化之前，持续保有其科研价值。即便在引力波背景被成功探测之后，我们仍需持续开展观测，以支撑引力波天文学这一新兴领域的发展！