Parkes observations for project P1211 semester 2023OCTS_04

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.

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.

传统的脉冲星搜寻技术对极端脉冲星的探测灵敏度不足，这类极端脉冲星包括密近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）、超高速自转脉冲星（例如亚毫秒脉冲星，sub-MSPs）以及高色散量（dispersion measure, DM）脉冲星（例如银心与银道面中的脉冲星）。随着澳大利亚平方千米阵列探路者（Australian Square Kilometer Array Pathfinder, ASKAP）等下一代射电望远镜阵列的发展，这一现状现已得到改观。ASKAP具备开展高灵敏度大天区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, EMU）。其中一种可行方案是在EMU等射电连续谱巡天项目中识别脉冲星候选体，随后开展针对性搜寻。该技术可让我们在全视场范围内对宽带宽进行搜寻，同时无需进行成本高昂的逐像素高时间分辨率搜索。

在本研究提案中，我们计划利用全新的ASKAP EMU图像，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的射电源，共得到23个候选体。其中7个为已知脉冲星，脉冲星候选体检出率高达约33%，剩余16个候选体的规模也适合开展后续跟进研究。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遗漏了这类MSP。为此，我们计划利用帕克斯UWL望远镜（Parkes UWL）开展针对性脉冲星搜寻，该设备可在更高频段探测脉冲信号，从而规避严重的DM弥散与散射效应。