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arXiv 2205.13435astro-ph.HE
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磁星对对称风中的法拉第转换与快速射电暴

Faraday conversion in pair-symmetric winds of magnetars and Fast Radio Bursts

Maxim Lyutikov

摘要:

我们考虑在成对对称磁星风的内部,靠近光柱的偏振传播。磁场中的成对等离子体是双折射的,是一种$\propto B^2$效应。因此,这样的等离子体就像相位延迟器一样工作:斯托克斯参数在庞加莱球上遵循圆形轨迹。在高磁化状态下,$ω, \, ω_p \ll ω_B$,相应的旋转速率与磁场无关。具有色散量度DM $\sim 10^{-6}$ pc cm $^{-3}$的等离子体屏可以引起大的偏振变化,包括大的有效旋转量度(RM)。(广义)RM的频率缩放,$ \propto λ^α$,模拟了具有小相移的$α=2$的常规RM,但是可以小到$α=1$。在解释观测时,极化参数的频率标度应独立拟合。该模型提供了以下解释:(i)在FRB中观察到的大圆偏振分量,具有左右切换;(ii)大RM,具有可能的符号变化;(iii)随时间变化的偏振。相对密集和缓慢的风是必要的-在规则的风中相应的影响很小。

英文摘要:

We consider propagation of polarization in the inner parts of pair-symmetric magnetar winds, close to the light cylinder. Pair plasmas in magnetic field is birefringent, a $\propto B^2$ effect. As a result, such plasmas work as phase retarders: Stokes parameters follow a circular trajectory on the Poincare sphere. In the highly magnetized regime, $ω, \, ω_p \ll ω_B$, the corresponding rotation rates are independent of the magnetic field. A plasma screen with dispersion measure DM $\sim 10^{-6}$ pc cm$^{-3}$ can induce large polarization changes, including large effective Rotation Measure (RM). The frequency scaling of the (generalized) RM, $ \propto λ^α$, mimics the conventional RM with $α=2$ for small phase shifts, but can be as small as $α=1$. In interpreting observations the frequency scaling of polarization parameters should be fitted independently. The model offers explanations for (i) large circular polarization component observed in FRBs, with right-left switching; (ii) large RM, with possible sign changes; (iii) time-depend variable polarization. Relatively dense and slow wind is needed - the corresponding effect in regular pulsars is small.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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