1.38GHz蟹状星云脉冲星偏振的高时间分辨率测量
High-Time-Resolution Measurements of the Polarization of the Crab Pulsar at 1.38 GHz
摘要：
使用韦斯特博克综合射电望远镜（WSRT），我们获得了高时间分辨率的测量的全（线和圆）偏振的螃蟹脉冲星。以34 ms脉冲周期的1/8192的分辨率获取（即，$4.1~μ{\rm s}$），1.38-GHz的线性极化测量与以前的较低的时间分辨率1.4-GHz的线性极化测量在主脉冲（MP），在脉冲间（IP），并在低频分量（LFC）一般协议。我们发现MP和IP在大约$24\%$和$21\%$处是线性偏振的，在偏振位置角上没有可辨别的差异。然而，与理论预期和在可见光测量相反，我们没有发现MP、IP或LFC上偏振位置角显著变化（扫描）的证据。尽管如此，主脉冲在线性偏振度上表现出小的但统计上显著的二次变化。我们讨论的影响，似乎是在矛盾的理论预期。此外，我们在主脉冲和脉冲间检测到弱圆偏振，在低频分量中检测到强（$\approx 20\%$）圆偏振，在与MP或IP的位置角约为$40\degree$的位置角处，低频分量也表现出非常强（$\approx 98\%$）的线偏振。脉冲平均偏振特性与LFC是低空分量和MP和IP是高空焦散分量一致。然而，目前的MP和IP发射模型不容易占观察到的整个脉冲的显着偏振变化的情况下。最后，我们测量IP和LFC脉冲相位相对于MP是一致的，与最近的测量，这表明这些脉冲分量的相位随时间的推移而发展。
英文摘要：
Using the Westerbork Synthesis Radio Telescope (WSRT), we obtained high-time-resolution measurements of the full (linear and circular) polarization of the Crab pulsar. Taken at a resolution of 1/8192 of the 34-ms pulse period (i.e., $4.1~μ{\rm s}$), the 1.38-GHz linear-polarization measurements are in general agreement with previous lower-time-resolution 1.4-GHz measurements of linear polarization in the main pulse (MP), in the interpulse (IP), and in the low-frequency component (LFC). We find the MP and IP to be linearly polarized at about $24\%$ and $21\%$, with no discernible difference in polarization position angle. However, and contrary to theoretical expectations and measurements in the visible, we find no evidence for significant variation (sweep) in polarization position angle over the MP, the IP, or the LFC. Although, the main pulse exhibits a small but statistically significant quadratic variation in the degree of linear polarization. We discuss the implications which appear to be in contradiction to theoretical expectations. In addition, we detect weak circular polarization in the main pulse and interpulse, and strong ($\approx 20\%$) circular polarization in the low-frequency component, which also exhibits very strong ($\approx 98\%$) linear polarization at a position angle about $40\degree$ from that of the MP or IP. The pulse-mean polarization properties are consistent with the LFC being a low-altitude component and the MP and IP being high-altitude caustic components. Nevertheless, current models for the MP and IP emission do not readily account for the observed absence of pronounced polarization changes across the pulse. Finally, we measure IP and LFC pulse phases relative to the MP that are consistent with recent measurements, which have shown that the phases of these pulse components are evolving with time.
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