arXiv 1302.46842013-02-19astro-ph.SR

$σ$ Orionis E的偏振观测

Polarimetric observations of $σ$ Orionis E

Alex C. Carciofi, Daniel M. Faes, Richard H. D. Townsend, Jon E Bjorkman

备注：: 5 pages, 4 figures, accepted for The Astrophysical Journal Letters
DOI：: 10.1088/2041-8205/766/1/L9

摘要：

一些大质量恒星拥有强大的磁场，将等离子体限制在星周环境中。这些\textit{magnetospheres}已被研究光谱，光度，最近，干涉。在这里，我们报告的第一个公司检测磁层连续线性极化，作为监测的结果$σ$ \，奥利\，E在皮科多斯迪亚斯天文台。{The非零的固有偏振表示不对称结构，其短伸长轴取向为天北以东的$150\fdg0$。观察到的偏振调制，与旋转周期的一半，这支持的理论预测的存在下，两个直径相对，共同旋转的气体斑点的周期。在光变曲线的偏振最小值和主最小值之间检测到-0.085的相位滞后，表明等离子体云的复杂形状。我们提出了一个初步的分析数据与刚性旋转磁层模型，它不能同时再现的光度和偏振数据。一个玩具模型，包括两个球形共同旋转的斑点{加入一个薄盘}证明更成功地再现偏振调制。{With通过这个模型，我们能够确定薄圆盘的总散射质量与斑点的质量（$2M_{\rm b}/M_{\rm d}=1.2$）相似，并且斑点在天空平面上逆时针旋转。这一结果表明，偏振测量可以提供一个诊断的云的几何形状，这将是一个重要的约束{改进}的刚性旋转磁层模型。

英文摘要：

Some massive stars possess strong magnetic fields that confine plasma in the circumstellar environment. These \textit{magnetospheres} have been studied spectroscopically, photometrically and, more recently, interferometrically. Here we report on the first firm detection of a magnetosphere in continuum linear polarization, as a result of monitoring of $σ$\,Ori\,E at the Pico dos Dias Observatory. {The non-zero intrinsic polarization indicates an asymmetric structure, whose minor elongation axis is oriented $150\fdg0$ east of the celestial north.} A modulation of the polarization was observed, with a period of half of the rotation period, which supports the theoretical prediction of the presence of two diametrally opposed, co-rotating blobs of gas. A phase lag of -0.085 was detected between the polarization minimum and the primary minimum of the light curve, suggestive of a complex shape of the plasma clouds. We present a preliminary analysis of the data with the Rigidly Rotating Magnetosphere model, which could not reproduce simultaneously the photometric and polarimetric data. A toy model comprising two spherical co-rotating blobs {joined by a thin disk} proved more successful in reproducing the polarization modulation. {With this model we were able to determine that the total scattering mass of the thin disk is similar to the mass of the blobs ($2M_{\rm b}/M_{\rm d}=1.2$) and that the blobs are rotating counterclockwise on the plane of the sky.} This result shows that polarimetry can provide a diagnostic of the geometry of clouds, which will serve as an important constraint for {improving} the Rigidly Rotating Magnetosphere model.

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