Parkes observations for project P1078 semester 2020OCTS_01

Black-Widow (BW) millisecond pulsars (MSPs) form a special subclass of MSPs having a low mass companion (~0.01-0.05 solar mass) in compact binary orbit with orbital period < 10 hours. Material blown from the companion by relativistic pulsar wind causes frequency dependent eclipses of the pulsar radio emission. Among these known eclipsing BW MSPs we have chosen three relatively bright objects which show eclipses at relatively higher radio frequencies. We request 30 hours observing time to observe these pulsars with Parkes UWL receiver in 700-4032 MHz to achieve the following science goals,\r\n i) With wideband observations of these pulsars we will apply a technique of modelling the eclipse phase spectra (already demonstrated by us) in optically thick to thin transition state (optical depth ~1), which will in turn allow to directly probe to the eclipse material.\r\nii) Simultaneous polarisation observations will allow us to predict the magnetic field strength in the eclipse boundaries through measurements of the rotation measure . Derived magnetic field strengths at the eclipse boundaries will be compared with the values from modelling the eclipse phase spectra. This will allow us to solve the existing puzzle of few orders of magnitude lower magnetic field strength at eclipse boundaries to withstand the pulsar wind ram pressure.\r\niii) Modelling the spectra at different orbital phases over the eclipse will allow us to probe the eclipse material properties and eclipse mechanism at different orbital phases, which is a new way to probe the pulsar and stellar wind interaction.

黑寡妇（Black-Widow, BW）毫秒脉冲星（millisecond pulsars, MSPs）是一类特殊的毫秒脉冲星子类，其拥有轨道周期小于10小时的致密双星轨道，伴星质量约为0.01~0.05倍太阳质量。相对论脉冲星风从伴星剥离的物质，会导致脉冲星射电辐射出现频率依赖性掩食。在已知的这类掩食型黑寡妇毫秒脉冲星中，我们选取了3颗相对明亮且在较高射电频段呈现掩食现象的源。我们申请了30小时的观测时长，计划使用帕克斯（Parkes）UWL接收机在700~4032 MHz频段对这些脉冲星开展观测，以达成以下科学目标：
i) 通过对这些脉冲星的宽频观测，我们将运用已由本团队验证过的掩食阶段光谱建模技术，针对光厚至光薄的过渡状态（光学深度约为1）开展建模，从而直接探测掩食物质的特性。
ii) 同步开展的偏振观测将使我们能够通过转动量（rotation measure）的测量结果，预测掩食边界处的磁场强度。我们会将掩食边界处推导出的磁场强度与掩食阶段光谱建模得到的数值进行对比，以此解决当前存在的谜题：为何掩食边界处的磁场强度比理论所需值低数个数量级，却足以抵御脉冲星风的动压。
iii) 对掩食过程中不同轨道相位下的光谱进行建模，将使我们能够探究不同轨道相位下的掩食物质特性与掩食机制，这为研究脉冲星与恒星风的相互作用提供了全新的途径。