Parkes observations for project P1021 semester 2020APRS_08

We propose to continue our observations of PSR J1653-45, a 951-ms pulsar in a long, 1.5-yr orbit. Binary pulsars are valuable objects of scientific study, allowing for a wide range of applications, including tests of gravity, probes of the neutron star equation of state, and fossil records of stellar evolution. Long spin-period pulsars in binary systems are generally much rarer than faster-spinning `recycled’ pulsars, and represent an under-explored region of pulsar binary evolution.\r\n\r\nIn addition to its long orbital period, PSR J1653-45 also experiences extended eclipses, lasting up to half of the orbital period and whose nature is not well understood. These eclipses have also prevented the determination of an orbital or phase-connected timing solution, both vital steps in allowing for the continued study of this system. We propose a targeted, high-cadence observing campaign designed to monitor this pulsar as it transitions out of its eclipsing state. The campaign has the twin goals of both monitoring how the eclipse affects the pulsar’s emission properties, thereby revealed more about the nature of the eclipses themselves, and of extracting as much information regarding the pulsar’s orbit during its least-explored regions, thereby constrained and hopefully solving the pulsar’s orbit and ideally leading to the development of a timing solution. In both instances, we hope to gain a greater understanding of this pulsar’s properties and how it fits into this under-explored class of unrecycled pulsar binaries.

我们提议开展对脉冲星PSR J1653-45的持续观测。该天体自旋周期为951毫秒，处于时长达1.5年的长周期双星轨道中。双星脉冲星是极具科研价值的研究对象，可应用于诸多科学场景，包括引力检验、中子星物态方程探测以及恒星演化化石记录研究等。双星系统中长自旋周期脉冲星通常远少于快速旋转的“再循环脉冲星（recycled pulsar）”，且代表了脉冲星双星演化领域中一个尚未被充分探索的研究方向。

除拥有较长轨道周期外，脉冲星PSR J1653-45还会出现持续时长可达轨道周期一半的延长食现象，其本质目前尚未得到清晰阐释。此类食现象也阻碍了轨道参数与相位关联计时解（phase-connected timing solution）的确定，而这二者皆是对该系统开展持续研究的关键步骤。为此我们提出一项针对性的高重频观测计划（high-cadence observing campaign），旨在监测该脉冲星从食态向正常辐射态的转变过程。本观测计划兼具双重目标：其一为探明食现象对脉冲星辐射特性的影响，以此进一步揭示食现象的本质；其二为在该系统最少被探索的轨道阶段，尽可能提取脉冲星轨道相关信息，以期约束并最终确定该脉冲星的轨道参数，进而推动计时解的建立。通过上述两项研究，我们期望能够更深入地理解该脉冲星的物理特性，以及它在这一尚未被充分探索的非再循环双星脉冲星类别中所处的位置。