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arXiv 1609.00640astro-ph.HEastro-ph.CO
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RoboPol:gamma-ray --大声的和gamma-ray --安静的耀变体的光学偏振

RoboPol: The optical polarization of gamma-ray--loud and gamma-ray--quiet blazars

E. Angelakis, T. Hovatta, D. Blinov, V. Pavlidou, S. Kiehlmann, I. Myserlis, M. Boettcher, P. Mao, G. V. Panopoulou, I. Liodakis, O. G. King, M. Balokovic, A. K… 展开作者

E. Angelakis, T. Hovatta, D. Blinov, V. Pavlidou, S. Kiehlmann, I. Myserlis, M. Boettcher, P. Mao, G. V. Panopoulou, I. Liodakis, O. G. King, M. Balokovic, A. Kus, N. Kylafis, A. Mahabal, A. Marecki, E. Paleologou, I. Papadakis, I. Papamastorakis, E. Pazderski, T. J. Pearson, S. Prabhudesai, A. N. Ramaprakash, A. C. S. Readhead, P. Reig, K. Tassis, M. Urry, J. A. Zensus

摘要:

我们目前的平均R波段optopolarimetric数据,以及变异性参数,从第一和第二RoboPol观测季节。我们调查是否伽马射线-响亮和伽马射线-安静耀变体表现出系统的光学偏振特性的差异。我们发现,伽玛射线暴耀变体有一个系统性较高的偏振分数(0.092)比伽玛射线宁静耀变体(0.031),与假设的两个样本是从相同的偏振分数分布被拒绝在3σ水平。我们没有发现任何证据表明这种差异与红移分布、静止坐标系R带亮度密度或源分类的差异有关。中值偏振分数与同步加速器峰值频率的关系曲线示出了包络,这意味着高同步加速器峰值源具有集中在较低值周围的中值偏振分数的较小范围。我们的伽马射线-安静的来源显示出类似的中值极化分数,虽然它们都是低同步加速器峰值。我们还发现偏振角的随机性与同步辐射峰值频率有关.对于高同步加速器峰值源,其倾向于集中在优选方向周围,而对于低同步加速器峰值源,其更易变并且不太可能具有优选方向。我们提出了一个方案,介导有效的粒子加速冲击,并增加了螺旋B-场分量的冲击下游。

英文摘要:

We present average R-band optopolarimetric data, as well as variability parameters, from the first and second RoboPol observing season. We investigate whether gamma- ray--loud and gamma-ray--quiet blazars exhibit systematic differences in their optical polarization properties. We find that gamma-ray--loud blazars have a systematically higher polarization fraction (0.092) than gamma-ray--quiet blazars (0.031), with the hypothesis of the two samples being drawn from the same distribution of polarization fractions being rejected at the 3σ level. We have not found any evidence that this discrepancy is related to differences in the redshift distribution, rest-frame R-band lu- minosity density, or the source classification. The median polarization fraction versus synchrotron-peak-frequency plot shows an envelope implying that high synchrotron- peaked sources have a smaller range of median polarization fractions concentrated around lower values. Our gamma-ray--quiet sources show similar median polarization fractions although they are all low synchrotron-peaked. We also find that the random- ness of the polarization angle depends on the synchrotron peak frequency. For high synchrotron-peaked sources it tends to concentrate around preferred directions while for low synchrotron-peaked sources it is more variable and less likely to have a pre- ferred direction. We propose a scenario which mediates efficient particle acceleration in shocks and increases the helical B-field component immediately downstream of the shock.

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