Parkes observations for project P1168 semester 2023APRS_08

We discovered seven pulsars in the globular cluster Terzan 1 with the Green Bank Telescope (GBT), the first pulsars to be found in this cluster. The discoveries include five fully-recycled millisecond pulsars (MSPs) with spin periods between 3 and 6 ms, an 11-ms MSP, and a pulsar with an unusually long spin period of 134 ms. Our preliminary timing suggested that all seven are likely isolated pulsars, consistent with Terzan 1 being a core-collapsed globular cluster. The 134-ms pulsar is an especially interesting discovery in the context of pulsar formation via electron-capture rather than core-collapse supernovae. We observed Terzan 1 at Parkes with the UWL receiver in 2022OCT to test whether the pulsars could be detected and thus timed at Parkes. All seven pulsars are significantly detected in both observations. We propose a year-long timing campaign with Parkes/UWL to obtain phase-connected timing solutions for these pulsars; we request continuing status to continue these timing observations through 2023OCT. To refine the timing parameters and probe the pulsars' acceleration in the cluster potential, we will extend phase connection beyond one year using the 2022OCT observations, and we will attempt to phase connect back to the original GBT discovery pointings. In addition to timing, we will probe the pulsars' polarization properties and the Galactic magnetic field in the direction of Terzan 1; and the proposed observations will also be searched for new pulsars that may have been missed in previous observations.

我们利用绿岸望远镜（Green Bank Telescope, GBT）在球状星团Terzan 1中发现了7颗脉冲星，这是该星团中首次被发现的脉冲星。本次发现包含5颗完全再循环的毫秒脉冲星（millisecond pulsars, MSPs），其自转周期介于3至6毫秒之间，另有1颗自转周期为11毫秒的毫秒脉冲星，以及1颗自转周期长达134毫秒的特殊脉冲星。我们的初步计时分析显示，这7颗脉冲星均为孤立脉冲星，这与Terzan 1作为核塌缩球状星团（core-collapsed globular cluster）的属性一致。其中这颗134毫秒的脉冲星尤为引人注目，其对应的脉冲星形成机制契合通过电子俘获超新星（electron-capture supernova）而非核心塌缩超新星（core-collapse supernova）形成脉冲星的理论框架。
我们于2022年10月使用UWL接收机在帕克斯望远镜（Parkes）上对Terzan 1开展观测，以验证这些脉冲星能否在帕克斯望远镜上被探测并开展计时研究。本次帕克斯观测与此前的绿岸望远镜观测均显著探测到了全部7颗脉冲星。
我们提议开展为期一年的帕克斯/UWL计时观测项目，以获取这些脉冲星的相位连接计时解；同时申请延续观测状态，将计时观测持续至2023年10月。为优化计时参数并探究脉冲星在星团引力势场中的加速度，我们将结合2022年10月的观测数据将相位连接时长延长至一年以上，并尝试回溯至最初的绿岸望远镜发现观测时段完成相位连接。
除计时研究外，我们还将探测脉冲星的偏振特性以及Terzan 1方向的银河系磁场（Galactic magnetic field）；同时将在本次提议的观测中搜寻此前观测中可能遗漏的新脉冲星。