Parkes observations for project P1317 semester 2024OCTS_02

The existence of a population of millisecond pulsars (MSPs) in the Galactic bulge is supported, among others, by the Fermi GeV excess, a signal of gamma rays coming from the Galactic center (GC) direction and resembling the cumulative emission of known MSPs. A previous study showed that, while these MSPs are unresolved in gamma rays, some of them could have been detected in past X-ray observations. The authors also identified a large number of MSP candidates among unidentified X-ray sources. By analyzing unpublished radio images, we found interesting radio counterparts to 6 of those candidates, and were granted 20h of observations with the Green Bank Telescope to settle on their nature. We discovered two new MSPs, PSR J1740-2807 and PSR J1740-2805, towards one of our radio/X-ray targets, bringing to 4 the number of highly-dispersed MSPs in the GC direction and probably unveiling the first direct evidence of a bulge MSP population. We propose to carry out regular timing of these pulsar with Parkes, in order to reveal their properties and potentially claim association of PSR J1740-2807 with the original X-ray source. The follow up of these sources will have a major impact on our understanding of the Fermi GeV excess.

银河系银核球中存在毫秒脉冲星（millisecond pulsars, MSPs）群体这一结论，除其他佐证外，得到了费米GeV超出（Fermi GeV excess）现象的支持——该现象表现为来自银心（Galactic center, GC）方向的伽马射线（gamma rays）信号，其形态与已知毫秒脉冲星的累积辐射高度相似。此前的研究表明，尽管这些毫秒脉冲星在伽马射线波段无法被分辨，但其中部分天体可通过过往的X射线（X-ray）观测被探测到。研究团队还在未被证认的X射线源中识别出了大量毫秒脉冲星候选体。我们通过分析未公开的射电图像，为其中6个候选体找到了颇具研究价值的射电对应体，并获批使用绿岸望远镜（Green Bank Telescope）开展20小时的观测以确定这些天体的本质。我们在一个射电/X射线联合观测目标方向上发现了两颗新的毫秒脉冲星：PSR J1740-2807与PSR J1740-2805，使得银心方向高度弥散的毫秒脉冲星数量增至4颗，且该发现或许首次直接证实了银核球处存在毫秒脉冲星群体。我们提议使用帕克斯望远镜（Parkes）对这些脉冲星开展常规计时观测，以揭示其物理性质，并有望证认PSR J1740-2807与原始X射线源的对应关系。对这些天体的后续研究，将极大推动我们对费米GeV超出现象的认知。