论文标题
积聚脉冲星X-3的X射线极化图
The X-ray polarimetry view of the accreting pulsar Cen X-3
论文作者
论文摘要
CEN X-3是50年前发现的第一个X射线脉冲星。由于在存在强磁场的存在下，由于血浆和真空的繁殖与光子的传播相关，因此预计来自此类物体的辐射将高度极化。在这里，我们介绍了使用成像X射线极化探索器进行的CEN X-3观察结果的结果。源表现出明显的通量变异性，在两种状态下观察到了大约20倍的通量。在低亮度状态下，在脉冲平均（3 $σ$上限为12％）或相位分辨数据（3 $σ$上限为20-30％）中，没有发现显着极化。在明亮的状态下，极化度为5.8 $ \ pm $ 0.3％，极化角度为$ 49.6°\ pm1.5°$，其显着性约为20 $σ$，是通过对相位平衡数据的Spectro Polarimetrictric分析来测量的。相分辨分析显示通量和极化程度和极化角度的强变化之间存在显着的抗相关性。与旋转矢量模型的拟合表明，脉冲星旋转轴的位置角约为49 $°$，磁性倾斜为17 $°$。如果中子恒星表面的上层被吸积物质过热，并且极化模式的转化发生在上部热层和凉爽的下层大气层之间的过渡区域内，则可以解释相对较低的极化。偏振信号的一部分也可以通过从中子星表面和吸积窗帘反射的辐射来产生。
Cen X-3 is the first X-ray pulsar discovered 50 years ago. Radiation from such objects is expected to be highly polarized due to birefringence of plasma and vacuum associated with propagation of photons in presence of the strong magnetic field. Here we present results of the observations of Cen X-3 performed with the Imaging X-ray Polarimetry Explorer. The source exhibited significant flux variability and was observed in two states different by a factor of ~20 in flux. In the low-luminosity state no significant polarization was found either in pulse phase-averaged (with the 3$σ$ upper limit of 12%) or phase-resolved data (the 3$σ$ upper limits are 20-30%). In the bright state the polarization degree of 5.8$\pm$0.3% and polarization angle of $49.6°\pm1.5°$ with significance of about 20$σ$ was measured from the spectro-polarimetric analysis of the phase-averaged data. The phase-resolved analysis showed a significant anti-correlation between the flux and the polarization degree as well as strong variations of the polarization angle. The fit with the rotating vector model indicates a position angle of the pulsar spin axis of about 49$°$ and a magnetic obliquity of 17$°$. The detected relatively low polarization can be explained if the upper layers of the neutron star surface are overheated by the accreted matter and the conversion of the polarization modes occurs within the transition region between the upper hot layer and a cooler underlying atmosphere. A fraction of polarization signal can also be produced by reflection of radiation from the neutron star surface and the accretion curtain.
