论文标题
180 $^\ circ $在极化角度的旋转
180$^\circ$ Rotations in the Polarization Angle for Blazars
论文作者
论文摘要
在大麻中的电矢量位置角（EVPA）的旋转通常接近180 $^\ Circ $的整体倍数。文献中有许多例子，我们在这里分析了Robopol Monitoring计划的光学极化数据，通过表明$Nπ$旋转发生的频率比偶然性预期的频率更高，从而增强了证据。我们用一个由两个极化发射组成的模型来解释这一点：一个恒定时间的“喷气机”和一个可变的“爆发”。组合的EVPA在开始的开始和结束时都是$ \ rm evpa_ {JET} $，因此跨爆发的净旋转必须为$nπ$。在Stokes平面上分析了示例，其中组合的Stokes矢量的绕组数给出了$ n $的值。主要的结论是，EVPA旋转可能比围绕射流轴的发射区域的物理旋转大得多，但这需要射流的EVPA和爆发几乎是正交的。 Zhang等人的减震器计算。可以为我们的玩具模型提供物理模型，并自动提供所需的正交性。该模型用Myserlis等人发表的OJ287的数据进行了说明，我们建议看到的大型快速EVPA旋转可能存在相位效应，而不能代表物理旋转。
Rotations of the electric vector position angle (EVPA) in blazars are often close to an integral multiple of 180$^\circ$. There are multiple examples of this in the literature, and our analysis here, of the optical polarization data from the RoboPol monitoring program, strengthens the evidence by showing that $nπ$ rotations occur more frequently than expected by chance. We explain this with a model consisting of two polarized emission components: a "jet" that is constant in time, and a "burst" that is variable. The EVPA of the combination is $\rm EVPA_{jet}$ at both the beginning and the end of the burst, so the net rotation across the burst must be $nπ$. Examples are analyzed on the Stokes plane, where the winding number for the Stokes vector of the combination gives the value of $n$. The main conclusion is that the EVPA rotation can be much larger than the physical rotation of the emission region around the axis of the jet, but this requires the EVPAs of the jet and the burst to be nearly orthogonal. A shock-in-jet calculation by Zhang et al. can provide a physical model for our toy model, and in addition automatically gives the needed orthogonality. The model is illustrated with data on OJ287 published by Myserlis et al., and we suggest that the large rapid EVPA rotation seen there might be a phase effect and not representative of a physical rotation.
