Parkes observations for project P1317 semester 2024OCTS_05

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 By analyzing unpublished radio images, we found interesting radio counterparts to 6 of those candidates, and were granted 20h of observations with the Green Bank Telescope to settle on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.

银河系核球存在毫秒脉冲星（millisecond pulsars, MSPs）种群这一观点，除其他佐证外，还得到费米GeV超出（Fermi GeV excess）的支持——该信号为来自银心（Galactic center, GC）方向的伽马射线辐射，其谱形与已知毫秒脉冲星的累积辐射高度相似。此前一项研究显示，尽管这类毫秒脉冲星在伽马射线波段尚未被分辨，但其中部分已在过往的X射线观测中被探测到。该研究团队还在未证认的X射线源中识别出大量毫秒脉冲星候选体。通过分析未公开的射电图像，我们为其中6个候选体找到了极具科学价值的射电对应体，并获批使用绿岸望远镜（Green Bank Telescope）开展20小时的观测以确定其本质。我们在其中一个射电/X射线候选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，且很可能首次直接揭示了核球毫秒脉冲星种群的存在证据。我们提议利用帕克斯望远镜（Parkes）对这些脉冲星开展常规计时观测，以探明其物理性质，并有望证实PSR J1740-2807与原始X射线源的关联。对这些天体的后续研究，将显著加深我们对费米GeV超出现象的理解。