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arXiv 1905.03080astro-ph.HE
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旋转射电瞬变的极化研究

Polarization studies of Rotating Radio Transients

M. Caleb, W. van Straten, E. F. Keane, A. Jameson, M. Bailes, E. D. Barr, C. Flynn, C. D. Ilie, E. Petroff, A. Rogers, B. W. Stappers, V. Venkatraman Krishnan, P. Weltevrede

摘要:

利用64 m Parkes射电望远镜研究了22个已知的旋转射电瞬变(RRAT)的偏振特性,给出了17个RRAT的法拉第旋转测度(RM),其中17个RRAT的线偏振通量超过关脉冲噪声3 $σ$。使用跨越最大可测量范围$\pm1.18 \times 10^5 \, \mathrm{rad \, m^2}$(步长为1 $\mathrm{rad \, m^2}$)的试验RM的强力搜索,然后使用迭代细化算法,估计每个RM。测量的RRAT RM在|RM| $\sim 1$到$\sim 950$ rad m $^{-2}$的范围内,平均线性偏振分数为$\sim 40$ %。观察到单个脉冲高达100%线性偏振。RRAT的RM和相应的推断的平均磁场(平行于视线和自由电子密度加权)被观察到与银河系平面脉冲星人口是一致的。法拉第旋转分析通常是在积累的脉冲星数据上进行的,对于这些数据,已经整合了数百到数千个脉冲,而不是单个脉冲。因此,我们验证了迭代细化算法进行蒙特卡罗模拟的人工单脉冲在很宽的范围内的S/N和RM。在线性偏振通量的S/N为17及以上时,迭代细化100%地恢复了模拟RM值,其典型平均不确定度为$\sim5$ rad m $^{-2}$。这里描述和验证的方法也已成功地用于确定可靠的RM的几个快速无线电爆发(FRB)发现在帕克斯。

英文摘要:

We study the polarization properties of 22 known rotating radio transients (RRATs) with the 64-m Parkes radio telescope and present the Faraday rotation measures (RMs) for the 17 with linearly polarized flux exceeding the off-pulse noise by 3$σ$. Each RM was estimated using a brute-force search over trial RMs that spanned the maximum measurable range $\pm1.18 \times 10^5 \, \mathrm{rad \, m^2}$ (in steps of 1 $\mathrm{rad \, m^2}$), followed by an iterative refinement algorithm. The measured RRAT RMs are in the range |RM| $\sim 1$ to $\sim 950$ rad m$^{-2}$ with an average linear polarization fraction of $\sim 40$ per cent. Individual single pulses are observed to be up to 100 per cent linearly polarized. The RMs of the RRATs and the corresponding inferred average magnetic fields (parallel to the line-of-sight and weighted by the free electron density) are observed to be consistent with the Galactic plane pulsar population. Faraday rotation analyses are typically performed on accumulated pulsar data, for which hundreds to thousands of pulses have been integrated, rather than on individual pulses. Therefore, we verified the iterative refinement algorithm by performing Monte Carlo simulations of artificial single pulses over a wide range of S/N and RM. At and above a S/N of 17 in linearly polarized flux, the iterative refinement recovers the simulated RM value 100 per cent of the time with a typical mean uncertainty of $\sim5$ rad m$^{-2}$. The method described and validated here has also been successfully used to determine reliable RMs of several fast radio bursts (FRBs) discovered at Parkes.

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