Parkes observations for project P1211 semester 2024APRS_21

Traditional pulsar searching techniques are not sensitive enough to extreme pulsars such as millisecond pulsars (MSPs) in compact binaries (e.g., Pulsar-Blackhole binary systems), extremely fast spinning pulsars (e.g., sub-MSPs), and high dispersion measure (DM) pulsars. Such a situation is now changed thanks to the development of next generation radio telescope arrays such as Australian Square Kilometer Array Pathfinder (ASKAP). ASKAP is capable of conducting highly sensitive radio continuum surveys with wide sky coverage (e.g, Evolutionary Map of The Universe survey). One of the solutions is to find pulsar candidates in radio continuum surveys such as ASKAP surveys and then carry out targeted searches. This technique allows us to search over the wide bandwidth with full field of view while avoiding the need for expensive pixel-by-pixel high time resolution searches. In this proposal, we propose to observe 16 pulsar candidates identified in the Galactic plane using new ASKAP EMU images. We found 22 candidates by selecting sources with spectral index steeper than -2.0 and compactness less than 1.2. Among them 13 are known pulsars and a reasonable number of candidates to follow up (9 sources). In total, we have 16 candidates including seven sources from 2023APRS semester. Because of the dense ionised medium in the Galactic Plane, MSPs are likely to be missed by previous pulsar surveys carried out at 1.4 GHz. Here, we propose a targeted pulsar search with the Parkes UWL which allow us to search pulsation at higher frequencies and therefore avoid strong DM smearing and scattering effects.传统脉冲星搜索技术对极端脉冲星的探测灵敏度存在不足，这类极端脉冲星包括密近双星系统（compact binaries）中的毫秒脉冲星（millisecond pulsars, MSPs，例如脉冲星-黑洞双星系统（Pulsar-Blackhole binary systems））、超快旋转脉冲星（例如亚毫秒脉冲星（sub-MSPs））以及高色散量（dispersion measure, DM）脉冲星。随着下一代射电望远镜阵列技术的发展，以澳大利亚平方千米阵列探路者（Australian Square Kilometer Array Pathfinder, ASKAP）为代表的设备改变了这一现状。ASKAP可开展高灵敏度射电连续谱巡天（radio continuum surveys），具备大天区覆盖能力，例如宇宙演化地图（Evolutionary Map of the Universe, EMU）巡天。其中一种可行方案是在ASKAP巡天等射电连续谱巡天中搜寻脉冲星候选体（pulsar candidates），随后开展针对性搜索。该技术可在全视场（full field of view）范围内对宽频带进行搜寻，同时无需开展成本高昂的逐像素高时间分辨率（high time resolution）搜索。在本研究提案中，我们计划利用ASKAP获取的全新EMU图像，对银道面（Galactic plane）中已识别出的16颗脉冲星候选体开展观测。我们通过筛选谱指数（spectral index）陡于-2.0且紧凑度（compactness）小于1.2的源，共找到22颗脉冲星候选体。其中13颗为已知脉冲星，另有9颗源具备后续观测价值。本次共计纳入16颗脉冲星候选体，其中7颗源自2023年APRS学期的观测样本。由于银道面存在稠密的电离介质，此前在1.4 GHz频段开展的脉冲星巡天很可能遗漏了毫秒脉冲星（MSPs）。为此，我们提出利用帕克斯UWL望远镜（Parkes UWL）开展针对性脉冲星搜索，该设备可在更高频段搜寻脉冲信号，从而规避严重的DM弥散（DM smearing）与散射效应（scattering effects）。