分类： 天文学 >> 天文学 提交时间： 2024-05-10 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Rotating Radio Transients (RRATs) are a relatively new subclass of pulsars that emit detectable radio bursts sporadically. We analyzed 10 RRATs observed using the Parkes telescope, with eight of these observed via the ultra-wide-bandwidth low-frequency (UWL) receiver. We measured the burst rate and produced integrated profiles spanning multiple frequency bands for three RRATs. We also conducted a spectral analysis on both integrated pulses and individual pulses of three RRATs. All of their integrated pulses follow a simple power law, consistent with the known range of pulsar spectral indices. Their average spectral indices of single pulses are −0.9, −1.2, and −1.0 respectively, which are within the known range of pulsar spectral indices. Additionally, we find that the spreads of single-pulse spectral indices for these RRATs (ranging from −3.5 to +0.5) are narrower compared to what has been observed in other RRATs. Notably, the average spectral index and scatter of single pulses are both relatively small. For the remaining five RRATs observed at the UWL receiver, we also provide the upper limits on fluence and flux density. In addition, we obtain the timing solution of PSR J1709-43. Our analysis shows that PSRs J1919+1745, J1709-43, and J1649-4653 are potentially nulling pulsars or weak pulsars with sparse strong pulses.
分类： 天文学 >> 天文学 提交时间： 2023-12-29
Dengke Zhou
Pei Wang
Di Li
Jianhua Fang
Chenchen Miao
Paulo C. C. Freire
Lei Zhang
Dandan Zhang
Huaxi Chen
Yi Feng
Yifan Xiao
Jintao Xie
Xu Zhang
Chenwu Jin
Han Wang
Yinan Ke
Xuerong Guo
Rushuang Zhao
Chenhui Niu
Weiwei Zhu
摘要： Globular clusters harbor numerous millisecond pulsars; however, the detection of long-period pulsars within these clusters has been notably scarce. The search for long-period pulsars encounters significant challenges due to pronounced red noise interference, necessitating the crucial step of red noise removal in the data preprocessing. In this study, we use running median filtering to mitigate red noise in multiple globular cluster datasets obtained through observations with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Additionally, we estimated the minimum detectable flux density of pulsars ($S_{ rm min}$) considering this processing step, resulting in a function depicting how $S_{ rm min}$ varies with different duty cycles and periods. Subsequently, a systematic search for long-period pulsars was conducted on the globular cluster datasets after red noise elimination. Ultimately, two isolated long-period pulsars were discovered in the M15 globular cluster, with periods of approximately 1.928451 seconds and 3.960716 seconds, both exhibiting remarkably low pulse duty cycles of around 1 %. Using archived data, we obtained timing solutions for these pulsars. Based on the timing results, their positions are found to be close to the center of the M15 cluster. On the $P- dot{P}$ diagram, they both lie below the spin-up line, suggesting that their recycling process was likely interrupted, leading them to become isolated pulsars. Moreover, in our current search, these very faint long-period pulsars are exclusively identified in M15, and one possible reason for this could be the relatively close proximity and extremely high stellar formation rate of M15. As observational data accumulate and search algorithms undergo iterative enhancements, the prospect of discovering additional long-period pulsars within globular clusters, such as M15, becomes increasingly promising.
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