Parkes observations for project P1168 semester 2023OCTS_05

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. In 2022OCT we observed Terzan 1 with Parkes three times and confirmed that all pulsars could be detected. We began a year-long timing campaign in the present semester, 2023APR, and were granted continuing status for that campaign. We request to continue timing these pulsars 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.

本研究利用绿岸望远镜（Green Bank Telescope, GBT）在球状星团（globular cluster）Terzan 1中发现了7颗脉冲星（pulsar），这是该星团中首次被发现的脉冲星。此次发现包含5颗自旋周期介于3至6毫秒之间的完全再循环毫秒脉冲星（millisecond pulsar, MSP）、1颗自旋周期为11毫秒的毫秒脉冲星，以及1颗自旋周期达134毫秒的超长周期脉冲星。我们的初步脉冲星计时（pulsar timing）分析显示，这7颗脉冲星均为孤立脉冲星，与Terzan 1属于核塌缩球状星团的结论一致。这颗134毫秒脉冲星的发现尤为引人关注，其形成机制或源于电子俘获超新星（electron-capture supernova）爆发，而非核心塌缩超新星（core-collapse supernova）爆发。2022年10月，我们利用帕克斯望远镜（Parkes Telescope）对Terzan 1开展了三次观测，确认所有7颗脉冲星均可被探测到。我们于2023年4月启动了为期一年的计时观测项目，并获得了该项目的延续资格，现申请将该项目延续至2023年10月。为优化计时参数并探究脉冲星在星团引力势中的加速度，我们将利用2022年10月的观测数据将相位连接（phase connection）时长延长至一年以上，并尝试将相位连接回溯至最初利用绿岸望远镜进行发现观测的指向时刻。除计时观测外，我们还将研究脉冲星的偏振特性（polarization properties）以及Terzan 1方向的银河磁场（Galactic magnetic field）；同时，我们也将对本次拟开展的观测数据进行搜寻，以寻找此前观测中可能遗漏的新脉冲星。