Parkes observations for project P1005 semester 2021APRS_03

We propose to conduct observations of PSR J1812-15, a 1-s pulsar in a 20.3-hr circular orbit around a light companion which also exhibits variable emission (turning `on’ and `off’). 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\nWe propose a two-pronged campaign designed to address individual aspects of PSR J1812-15’s behaviour. Firstly, although we have developed a binary solution as a consequence of previous P1005 observations, we are still unable to develop a phase-connected timing solution, a key step in understanding this pulsar and its binary formation process. We therefore propose a 6-month monitoring campaign intended to provide the additional constraint required to determine a unique solution. Secondly, we have identified a correlation between the pulsar’s detectability and its orbital phase, suggesting that an eclipse or other complex interaction between the pulsar and its binary companion is at least partially responsible for its variable emission. We propose to monitor a series of consecutive orbits so as to fully cover the pulsar’s orbital phase, exploiting the wide bandwidth of the UWL receiver to distinguish between variability due to the binary companion or other sources (e.g. intrinsic pulse nulling).

我们提议对脉冲星PSR J1812-15开展观测研究：该天体为周期1秒的脉冲星，正以20.3小时的圆轨道环绕一颗低质量伴星运行，且该伴星同样表现出可变辐射，即辐射状态会在“开启”与“关闭”间切换。二进制脉冲星（binary pulsars）是极具科学价值的研究对象，可应用于诸多研究方向，包括引力检验、中子星物态方程（neutron star equation of state）探测以及恒星演化化石记录研究。双星系统中的长自旋周期脉冲星，通常比快速旋转的再循环脉冲星（recycled pulsars）更为罕见，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。

我们提出一项双管齐下的观测计划，以分别解析脉冲星PSR J1812-15的各项行为特征。其一，尽管基于此前的P1005观测结果我们已得到双星轨道解，但目前仍无法获得相位连接的计时解（phase-connected timing solution）——这是厘清该脉冲星及其双星形成过程的关键步骤。为此，我们提议开展为期6个月的监测计划，以获取足够的额外约束条件，从而得到唯一确定的轨道解。其二，我们已发现该脉冲星的可探测性与其轨道相位存在相关性，这表明脉冲星与伴星之间发生的食（eclipse）现象或其他复杂相互作用，至少是其可变辐射产生的部分原因。我们计划对一系列连续轨道进行监测，以完整覆盖该脉冲星的所有轨道相位，并利用UWL接收机（UWL receiver）的宽带宽特性，区分由双星伴星引发的辐射变化与其他来源（例如脉冲本征消零（intrinsic pulse nulling））引发的变化。