磁星1 E 1547.0-5408：无线电频谱，偏振测量和定时
The magnetar 1E 1547.0-5408: radio spectrum, polarimetry, and timing
摘要：
利用Parkes望远镜和澳大利亚望远镜紧凑阵研究了异常X射线脉冲星1E1547.0 -5408（PSR J1550-5418）的射电辐射。脉冲星的通量密度在1.4和45 GHz之间大致相同，但显示出时间变化。辐射在45和3.2 GHz之间几乎100%线性偏振，但从2.3到1.4 GHz，它变得越来越去偏振。-1860 rad/m^2的旋转测量值是已知脉冲星中最大的，这意味着沿视线的平均磁场强度为2.7 microG。脉冲轮廓在所有观察到的频率下都是圆偏振的，在较低的频率下更是如此，在~15%的水平上。观测到的线偏振位置角随脉冲相位的摆动表明，在这颗中子星中，自转轴和磁轴几乎是一致的，而且它的射电辐射只能在很小的立体角内被探测到。定时测量表明，这颗2秒脉冲星的周期导数在6个月内增加了近40%。平坦的光谱以及通量密度和脉冲轮廓的变化让人想起XTE J1810-197的特性，XTE J1810-197是唯一已知的其他无线电发射磁星，与普通的无线电磁星相比是异常的。
英文摘要：
We have investigated the radio emission from the anomalous X-ray pulsar 1E 1547.0-5408 (PSR J1550-5418) using the Parkes telescope and the Australia Telescope Compact Array. The flux density of the pulsar is roughly the same between 1.4 and 45 GHz, but shows time variability. The radiation is nearly 100% linearly polarized between frequencies of 45 and 3.2 GHz, but from 2.3 to 1.4 GHz it becomes increasingly more depolarized. The rotation measure of -1860 rad/m^2 is the largest for any known pulsar, and implies an average magnetic field strength along the line of sight of 2.7 microG. The pulse profiles are circularly polarized at all frequencies observed, more so at lower frequencies, at the ~15% level. The observed swing of the position angle of linear polarization as a function of pulse phase suggests that in this neutron star the rotation and magnetic axes are nearly aligned, and that its radio emission is only detectable within a small solid angle. Timing measurements indicate that the period derivative of this 2 s pulsar has increased by nearly 40% in a 6-month period. The flat spectrum and variability in flux density and pulse profiles are reminiscent of the properties of XTE J1810-197, the only other known radio-emitting magnetar, and are anomalous by comparison with those of ordinary radio pulsars.
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