极端闪烁体PKS B1144-379的星际闪烁
Interstellar Scintillation of an Extreme Scintillator: PKS B1144-379
摘要：
塔斯马尼亚大学的塞杜纳射电望远镜已被用于研究BL Lac天体PKS B1144-379在6.7 GHz处的无线电通量密度的快速变化。在2003年至2011年期间，对这种极端闪烁体进行了大约9年的高频率监测。我们使用的结构函数创建的强度时间序列，以确定特征的时间尺度的变化。在每年的某些时期，特征时间尺度一直被观察到增加，表明通过星际散射屏闪烁的年度周期。最佳拟合的年周期模型表明，闪烁图案具有各向异性的结构，其散射屏的上限是在~0.84千秒差距的距离。较高的各向异性在一些年度周期拟合表明，在内在的源结构的变化可能会影响的变化时间尺度。我们发现，一个突出的年度周期只存在于某些年份的变化时间尺度，其他证据表明，核心是紧凑的。根据我们的测量，我们计算出核心的角尺寸在5.65-15.90 $μ$之间变化为（0.05-0.13 pc）。在2005年和2008年观测到的总通量密度的两次耀斑期间，核心部分被认为是最紧凑的。我们的结论是，长期的无线电通量密度的PKS B1144-379的变化是由于源的内在变化，这些影响我们的能力，以测量其变化的时间尺度的年度周期。
英文摘要：
The University of Tasmania Ceduna radio telescope has been used to investigate rapid variability in the radio flux density of the BL Lac object PKS B1144-379 at 6.7 GHz. High-cadence monitoring of this extreme scintillator was carried out over a period of approximately nine years, between 2003 and 2011. We have used structure functions created from the intensity time series to determine the characteristic timescale of the variability. The characteristic timescale is consistently observed to increase during certain periods of each year, demonstrating the annual cycle expected for scintillation through an interstellar scattering screen. The best-fitting annual cycle model for each year suggests that the scintillation pattern has an anisotropic structure and that the upper limit of its scattering screen is at a distance of ~0.84 kpc. Higher anisotropy in some of the annual cycle fits suggests that changes in the intrinsic source structure might be influencing the variability timescale. We found a prominent annual cycle is only present in the variability timescale for certain years where other evidence suggests that the core is compact. From our measurements, we calculated that the core angular size varied between 5.65-15.90 $μ$as (0.05-0.13 pc). The core component was found to be at its most compact during two flares in the total flux density, which were observed in 2005 and 2008. We conclude that the long-term variability in the radio flux density of PKS B1144-379 is due to intrinsic changes in the source and that these affect our ability to measure an annual cycle in its variability time scale.
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