论文标题
X射线毫秒的相对论旋转矢量模型
Relativistic rotating vector model for X-ray millisecond pulsars
论文作者
论文摘要
预计在吸收磁性中子恒星表面产生的X射线辐射将是强化的。极化载体与脉冲星相的挥杆可直接衡量源倾斜度和磁性倾斜度。在快速旋转的毫秒脉冲星的情况下，发射区域的相对论运动会导致极化平面的额外旋转。在这里，我们开发了一个相对论旋转的矢量模型，在该模型中，我们得出了极化角度的分析表达，这是Schwarzschild指标中相对论畸变和重力弯曲的脉冲星相的函数。我们表明，在快速脉冲的情况下，极化平面的旋转可以达到数十个度，从而强烈影响了偏振角相位的观察到的形状。旋转角几乎随旋转速率线性生长，但对中子星半径的敏感性较小。总体而言，这个角度甚至对于大斑点也很大。我们的结果对X射线极化的建模具有含义，即从即将进行的成像X射线极化计探索器以及增强的X射线时间和极化指标的增强成像中观察到的毫秒脉冲星。 X射线极化可能会改善来自脉冲轮廓建模的中子星质量和半径的约束。
The X-ray radiation produced on the surface of accreting magnetised neutron stars is expected to be strongly polarised. A swing of the polarisation vector with the pulsar phase gives a direct measure of the source inclination and magnetic obliquity. In the case of rapidly rotating millisecond pulsars, the relativistic motion of the emission region causes additional rotation of the polarisation plane. Here, we develop a relativistic rotating vector model, where we derive analytical expression for the polarisation angle as a function of the pulsar phase accounting for relativistic aberration and gravitational light bending in the Schwarzschild metric. We show that in the case of fast pulsars the rotation of the polarisation plane can reach tens of degrees, strongly influencing the observed shape of the polarisation angle's phase dependence. The rotation angle grows nearly linearly with the spin rate but it is less sensitive to the neutron star radius. Overall, this angle is large even for large spots. Our results have implications with regard to the modelling of X-ray polarisation from accreting millisecond pulsars that are to be observed with the upcoming Imaging X-ray Polarimeter Explorer and the enhanced X-ray Timing and Polarimetry mission. The X-ray polarisation may improve constraints on the neutron star mass and radius coming from the pulse profile modelling.
