Parkes observations for project P1021 semester 2020APRS_01

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.

我们提出将延续对PSR J1653-45的观测计划，该天体是一颗处于1.5年长轨道周期双星系统中的951毫秒脉冲星。双星脉冲星（binary pulsars）是极具科研价值的研究对象，可支撑多项前沿研究方向，包括引力检验、中子星物态方程（neutron star equation of state）探针以及恒星演化化石记录的挖掘。双星系统中长自转周期脉冲星通常远少于自转更快的“再循环脉冲星（recycled pulsars）”，属于脉冲星双星演化领域中尚未被充分探索的研究范畴。

除拥有较长轨道周期外，PSR J1653-45还会出现持续时长可达轨道周期一半的长时食现象，其物理本质目前尚未得到清晰阐释。此类食现象同时阻碍了轨道解与相位连接计时解（phase-connected timing solution）的确定，而二者均为持续研究该双星系统的关键前置步骤。我们提出一项靶向高频次观测计划，旨在监测该脉冲星从食态过渡至正常辐射态的全过程。该观测计划兼具双重科研目标：其一，追踪食现象对脉冲星辐射特性的影响，从而进一步揭示食现象的本质；其二，在脉冲星受食影响最小的观测窗口内，尽可能提取其轨道相关信息，以此约束并有望求解该脉冲星的轨道参数，最终目标是建立完整的相位连接计时解。通过上述两项研究内容，我们期望能够更深入地理解该脉冲星的物理特性，明确其在尚未被充分探索的非再循环脉冲星双星系统类别中的定位。