Parkes observations for project P1021 semester 2019OCTS_03

We propose to conduct 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 of 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 transition into 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.

我们提议对PSR J1653-45开展观测，该天体是一颗自转周期为951毫秒的脉冲星（pulsar），处于时长1.5年的长周期轨道中。双星脉冲星（binary pulsar）是极具科研价值的天体，可应用于诸多研究方向，包括引力检验、中子星（neutron star）物态方程探针以及恒星演化的化石记录。双星系统中的长自转周期脉冲星，通常远少于快自旋的“再循环”脉冲星，且属于脉冲星双星演化研究中尚未被充分探索的范畴。

除拥有较长轨道周期外，PSR J1653-45还会发生持续时长可达轨道周期一半的掩食（eclipse）现象，其本质目前尚未得到充分阐释。此类掩食同样阻碍了相位连接计时解的确定，而这是持续开展该系统研究的两项关键步骤。

为此我们提议实施一项靶向性高频率观测项目，旨在对该脉冲星进入掩食状态的过程进行监测。本项目兼具双重目标：一是监测掩食如何影响脉冲星的辐射特性，从而进一步阐明掩食现象的本质；二是在该脉冲星受研究最少的轨道阶段，尽可能提取其轨道相关信息，以期约束并最终确定该脉冲星的轨道参数，并最终得到相位连接计时解。

通过上述两项研究，我们期望能够更全面地认识该脉冲星的物理特性，厘清其在尚未被充分探索的非再循环双星脉冲星类别中的定位。