Parkes observations for project P1211 semester 2023OCTS_05

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 (e.g., pulsars in Galactic Centre and Galactic Plane). 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 EMU 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. \n \n In this proposal, we propose to observe 16 MSP candidates identified in the Galactic plane using new ASKAP EMU images. We found 23 candidates by selecting sources with spectral index steeper than -1.90 and compactness less than 1.2. Among them 7 are known pulsars giving us high fraction of pulsars (~33%) and a reasonable number of candidates to follow up (16 sources). 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.

传统脉冲星搜寻技术对于极端脉冲星的灵敏度存在不足，这类极端脉冲星包括致密双星系统中的毫秒脉冲星（millisecond pulsars, MSPs，例如脉冲星-黑洞双星系统）、极快速旋转脉冲星（例如亚毫秒脉冲星）以及高色散量（dispersion measure, DM）脉冲星（例如银心与银道面中的脉冲星）。如今随着澳大利亚平方千米阵探路者（Australian Square Kilometer Array Pathfinder, ASKAP）这类下一代射电望远镜阵列的发展，这一困境得到了扭转。ASKAP具备开展高灵敏度、宽天区覆盖的射电连续谱巡天的能力（例如宇宙演化地图巡天（Evolutionary Map of The Universe survey, EMU））。其中一种可行方案是在EMU等射电连续谱巡天项目中筛选脉冲星候选体，随后开展针对性搜寻。该技术可在全视场宽带宽范围内完成搜寻工作，同时无需进行成本高昂的逐像素高时间分辨率搜索。

在本提案中，我们计划利用ASKAP EMU的最新观测影像，对银道面中已识别出的16个MSP候选体开展观测。我们通过筛选谱指数陡于-1.90且紧凑度小于1.2的源，共找到23个候选体。其中7个为已知脉冲星，脉冲星占比高达约33%，同时剩余待后续跟进验证的候选体数量合理（共16个源）。由于银道面中存在致密的电离介质，此前在1.4 GHz频段开展的脉冲星巡天很可能会遗漏MSPs。在此我们提议，使用帕克斯UWL（Parkes UWL）开展针对性脉冲星搜寻，该设备可在更高频率下搜寻脉冲信号，从而规避严重的DM弥散与散射效应。