Parkes observations for project P1078 semester 2020OCTS_03

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，其拥有质量约为0.01~0.05倍太阳质量的低质量伴星，且处于轨道周期小于10小时的密近双星轨道中。相对论性脉冲星风剥离伴星物质会导致脉冲星射电辐射出现频率依赖性食掩。在已发现的这类食掩型BW毫秒脉冲星中，我们选取了3颗相对明亮且可在较高射电频率下观测到食掩的源。我们申请使用帕克斯（Parkes）UWL接收机，在700~4032兆赫兹频段对这些脉冲星开展总计30小时的观测，以达成以下科学目标：
i) 通过对这些脉冲星的宽带观测，我们将采用已由本团队验证过的食相光谱建模技术，针对光学深度约为1的光学厚至薄跃迁状态进行建模，进而直接探测食掩物质的性质。
ii) 同步开展的偏振观测将允许我们通过旋转量（rotation measure）测量，推算食掩边界处的磁场强度。我们将把该方法得到的食掩边界磁场强度与食相光谱建模得到的数值进行对比，以此解决当前存在的谜题：食掩边界处的磁场强度相较于抵御脉冲星风冲压力所需的数值低数个数量级，这一现象的成因尚未明确。
iii) 对食掩过程中不同轨道相位下的光谱进行建模，将帮助我们探究不同轨道相位下的食掩物质性质与食掩机制，这为研究脉冲星与恒星风的相互作用提供了全新的研究途径。