Parkes observations for project P1317 semester 2024OCTS_03

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 By analyzing unpublished radio images, we found interesting radio counterparts to 6 of those candidates, and were granted 20h of observations with the Green Bank Telescope to settle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

银河系银核凸起（Galactic bulge）区域存在毫秒脉冲星（millisecond pulsars, MSPs）种群这一假说，除其他佐证外，得到了费米GeV超出（Fermi GeV Excess）的支持：该信号源自银核（Galactic center, GC）方向的伽马射线辐射，其能谱特征与已知毫秒脉冲星的累积辐射高度吻合。此前一项研究表明，尽管这些毫秒脉冲星在伽马射线波段无法被分辨，但其中部分天体已在过往的X射线观测中被探测到。该研究团队还在未被证认的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个候选体找到了颇具研究价值的射电对应体，并获准使用绿岸望远镜（Green Bank Telescope）开展20小时的观测以确定它们的天体属性。我们在一个射电/X射线观测目标中发现了2颗新的毫秒脉冲星：PSR J1740-2807与PSR J1740-2805，使银核方向的高色散毫秒脉冲星数量增至4颗，这一发现或许首次为银核凸起区域存在毫秒脉冲星种群提供了直接观测证据。我们提议使用帕克斯望远镜（Parkes）对这两颗脉冲星开展常规计时观测，以揭示它们的物理属性，并有望证认PSR J1740-2807与原始X射线源的对应关系。对这些天体的后续观测，将极大推动我们对费米GeV超出现象的认知。